What is this vine?

Question: What is this vine?  I live in TX near San Antonio, it sprouts little flowers and then has these round black berries.  I really want to know because this vine has a mind of its own and will attach itself to items and grow.  Thank you all for your help I have been trying to identify for over a year.  I don't believe it is a
Comment: Welcome to the site!! It looks like your last sentence is unfinished. You were saying what you don't think it looks like something but that part is gone. Would you please add that to your question? Also, do you have a picture of it when it's flowering? That would help with the identification. Thank you!
Answer: I've been looking at this image on and off all day, trying to remember what it is. Luckily, it's now come to mind; it looks like Malabar Spinach, or more specifically, this particular  one's Basella rubra var. rubra. It's a vining plant with quite nutritious, edible leaves that are a bit like spinach, has white flowers, dark berries later on. Image and info here https://www.seedman.com/vine.htm but you'll need to scroll down a fair way - it's further down, under perennial vines. Frost tender and is also grown for purely ornamental reasons.
Comment: You got it, Bamboo. I had no idea Malabar spinach formed dark small berries! The vine site is nice too. Thinking of all the different vines I'd love to have practically makes me drool.

What is this vine?


Encryption Library for Arduino

Question: I am using an Arduino to read a keypad and open an electric strike upon keypad PIN entry. For this sketch I wanted to use some sort of lightweight encryption to store the PINs in EEProm.
Does anyone know of such a library? I have heard it may be possible using TwoFish.
Answer: You don't want to encrypt passwords (PINs) -- you want to hash them.  When someone enters a password, you hash that password, and compare the hash against the stored hash.  The advantage to this method (used for over 30 years) is that even if someone gets hold of the source and the hashes, they still can't tell what PINs match the hashes, as long as you choose a strong enough hash function.
You don't want to implement encryption yourself -- you want to use someone else's library, particularly one with an open implementation that has been tested by a large community.  Encryption is hard, testing is hard, and testing encryption is damned hard, so get someone else to do it for you.
You should checkout the AVR Crypto Library, which is licensed with GPLv3.  There's also an implementation of Skein for AVR.
Comment: Upvoted -- A good resource, and this should be set as the answer to the question.
Answer: That link Hristos posted, while possibly useful, certainly doesn't count as "encryption". It's really only "obfuscation".
Proper cryptography is notoriously easy to get wrong, even for people who know the math.
In response to the original post - what are the attack methods that would let someone get access to the PINs in the EEProm? Surely if they've got that far into your electronics they can just "snip the red wire" and open the door?
If you somehow do have a system where attackers might get hold of the EEProm contents without already having enough access to open your door, you probably want to redesign it. You could look at one-way hash functions similar to Unix password hashing - that way the EEProm doesn't need t contain a decryption key - the problem is the search space for PINs is very small - if I can download the hashed version of the PIN, I can pretty quickly try all 10,000 possible PINs, I suspect any modern-ish laptop will run all of them in a few seconds.
Comment: I agree (and agreed above), a one way hash would be useful and if you are programming the system then you could make the pin as long as you want eg 8 digits gives 100 000 000 combinations, which should take much longer.
Answer: Here is a method of simple encription in C that could easily be ported to the Arduino. This seems like the easiest way to encrypt data with the arduino's limited resources.
-EDIT- To keep the key out of your program you could make half of the PIN the key. This means that your program takes the key half of the PIN to decrypt the encrypted 1/2 PIN stored in EEProm. If the decrypted key from EEProm match the part of your pin that is not the key, the door would unlock. This would only work in a situation where it is not possible for the intruders to break down the door or reprogram the Arduino.
Comment: But if they have no access to your chip you don't need to encrypt the pin.
Answer: The problem I forsee is that if they can see your pins they can also see your program which encrypts/checks/decrypts your pins. Plus if they have your chip, can they not just alter the program to always give a positive result (effectively bypassing the check) for any pin entered.
Answer: How do you plan to decode the encrypted PINs, in order to check if the user entered a valid PIN? You'll need to store the decryption key...at which point if the attacker can read your eeprom, he can also read your flash to find the encryption key. Basically rendering your entire encryption completely useless. Also as the other people said, if he already has the ability to read your chip, he could just write a new program. Much simpler to just kick the door open, I doubt anyone would ever go to the trouble of trying to hack your chip.
Answer: These comments are really spot-on.  There's nothing wrong with trying to experiment to learn about encryption, but this isn't really a good project for learning such things.  You really want a good textbook and a computer, and as @bigiain says, the math is notoriously easy to get wrong.
For a better understanding of how cryptography works and what you're up against, the Handbook of Applied Cryptography is excellent and free:
If you just want to secure your project, this is an inefficient way of doing so.  If you're interested in cryptography, start with this book and a computer.
Comment: I understand cryptography, read Bruce Schneier, and have programmed for over twenty years. I understand the real threat is just breaking the door down and walking past any sort of Arduino controller. I just can't in good conscience install it with clear text PINs in teh EEProm if it can be avoided.
Fly
Comment: There's any number of simple obfuscation methods that would be just as effective in this role if you want to avoid storing clear-text PINs.  The responders above were only trying to help you understand what cryptography does and does not do.

Here's an AES library:
http://www.hoozi.com/Articles/AESEncryption.htm

I'd also like to say that just because you've programmed for 20 years, it doesn't mean you "understand" cryptography. It is a totally different field. A 20-year auto mechanic is a skilled person, but I wouldn't expect him to design a CAN bus from scratch.  Check your attitude, please.
Comment: Oh god... 20 years coding and you think it's possible to encrypt runtime data????? Quit.
Answer: I hate not answering the question while asking another, but ...
Is there some reason why your device is not tamper proof? I've seen push button switches in screw holes implemented 'on the bench' to detect the kind of tampering you are worried about. Then .. here comes the kid with a butane micro torch that manages to get your chip without unscrewing anything (or damaging the chip).. somehow, he knew the design of your tamper proof system which (also, hopefully) includes detecting changes in ambient light and / or sound. When the cover comes off, both become quite different .. day or night.
If that's the case, it should be a two part system where the exposed pieces communicate with something where encryption is more easily implemented. Plus, checksums (help) account for the kid with the torch.
I think you are asking a screwdriver to be a hammer.

Encryption Library for Arduino


Spiceworks versus Request Tracker?

Question: We currently utilize Request Tracker for help desk ticketing, we utilize Spiceworks for asset inventorying. I am pondering whether it might be worthwhile to move from RT to Spiceworks for help desk as well. Has anyone used both systems and can provide some insight into any benefits/problems with either system? Or has general philosophical reasons why one should use one solution over the other? Of course, RT is open source and Spiceworks is not - and usually this would be a major item for me - but since Spiceworks is free and takes community involvement fairly actively its not as major of a concern for me (personally).
Answer: Spiceworks works really well until it doesn't. As long as you're aware of its performance limitations, you'll be fine with it.
My organization is currently trying to roll out Spiceworks in a 1000+ user environment. We've been met with significant performance limitations because it can't utilize more than two cores, relies on a slow SQLite backend, and consumes high amounts of disk I/O. Their support is a bumbling nightmare when it comes to troubleshooting these, and so far their only solution has been for us to move our installation from a virtual server on our production VMware cluster with a robust FC SAN backend to a physical machine with slipshod consumer-level SSDs. Predictably, performance is worse in their recommended configuration than the one we were already using.
Feature-wise, though, it's a great product and totally worth using. It's very easy to customize and has a very robust third-party developer ecosystem. In its current state, though, it's just not fit for large environments at all.
Answer: I have been using Spiceworks for years in our production environment. We fully rely on it for our help desk operation for ticket tracking, asset management and monitoring. I has been one of the best products we have ever used in our department and it continues to grow and provide new features for us.
Answer: I would say to you what I say to everyone who has to pick between products.
What works for you? I use RT, and it does what I need it to do. I personally  prefer having small tools that do the job well, as opposed to one big tool, that does the job okay, and maybe with some brute force, do the job well! Reason, one part of that system dies, it all dies.
Use RT for what it was designed for, and use SPICEWORKS for what it is designed for :)
HTH

Spiceworks versus Request Tracker?


Does playing gambits improve your tactical skills?

Question: I once heard that you can sharpen your tactical skills by playing gambit openings?  If this is true, obviously you would and should improve your game.  Does anyone have any information or proof of this?
Comment: I think the goal is to play openings that lead to tactical positions, which is often achieved by playing tactical openings, of course. However, non-gambit openings can lead to tactical positions as well, for example playing open Sicilian is probably a better choice than playing Wing Gambit (`1.e4 c5 2.b4`).
Comment: IMO playing a gambit _would_ increase your skill because you're taking a risk that could get yourself into a bad position or behind materially.  This would lead to harder thinking and better tactical skills.
Comment: I agree with Seth's comment. I sometimes play the King's Gambit to lead the game into tactically rich positions. (You might want to play it safe instead against more advanced players than you)
Answer: I think that there are important skills you can learn from playing gambits, like how to use an advantage in development and the initiative, or just the fact that material isn't everything. It's probably also useful to learn those things early on in your chess career.
I'm not sure about them being better for improving tactics though. Every chess game has tactics.
Answer: Indeed, learning to part with material for minor and major positional advantages is a key in the recipe to learning to play on the "edge." In a gambit, the player who is ahead (gambitee) must eventually "give back" some material, otherwise risk getting in a losing position. The player who is behind in material (gambiter) usually enjoys greater maneuverability and tactical lines.
It is the goal of the gambiter to not necessarily trade back for the loss of material, but to gain a better position or a strong attack. It is the goal of the gambitee to "give back" the material in such a way that he does not weaken his own position, preferably he can strengthen it. The outcome of the gambit is usually determined by how sound the gambit is and which player has more patient: the gambitee should not overextend to defend the material gain, the gambiter should not seek to immediately reclaim lost material.
Comment: @Idog: I think sound gambits very often end that way. Soundness is a matter of how the game should end up theoretically, but in practice nobody is perfect and it's perfectly possible that the player with the extra material can hold on to it and win the endgame. I've won tens of Morra gambits as Black that way...
Comment: Why do you say "the player who is ahead (gambitee) must eventually "give back" some material" and "It is the goal of the gambitee to "give back" the material..."? It is fairly common that gambitee holds on the extra material, survives the attack, and gets to a winning endgame, and thus wins without ever giving back material.
Comment: It may be a personal observation, but rarely does a *sound* gambit end with a gimbitee winning endgame with the material they won. In such a case, I would label the gambit as *unsound*.


Improper integral; exponential divided by polynomial

Question: How can I evaluate $$\int_{-\infty}^\infty {\exp(ixk)\over -x^2+2ixa+a^2+b^2} dx,$$ where $k\in \mathbb R, a>0$? Would Fourier transforms simplify anything? I know very little about complex analysis, so I am guessing there is a rather simple way to evaluate this? Thanks.
Answer: You can evaluate this using the residue theorem. The integrand has simple poles at $x_\pm=\mathrm ia\pm b$ (which you can find by setting the denominator zero and solving the quadratic equation). You can find the residues at the poles by multiplying the integrand by $x-x_\pm$ and then substituting $x_\pm$, which yields
$$\left.-\frac{\exp(\mathrm ixk)}{x-(\mathrm ia\mp b)}\right|_{x=\mathrm ia\pm b}=\mp\exp(-ka)\frac{\exp(\pm\mathrm ikb)}{2b}\;.$$
If $k\gt 0$, You can complete the integral by a half circle at infinity in the upper half-plane (which contains the poles), since the integrand decays quadratically with $x\to\pm\infty$ and exponentially with $x\to\mathrm i\infty$, so the contribution from this half circle vanishes. Thus by the residue theorem the given integral is $2\pi\mathrm i$ times the sum of the residues, that is,
$$2\pi\mathrm i\left(-\exp(-ka)\frac{\exp(\mathrm ikb)}{2b}+\exp(-ka)\frac{\exp(-\mathrm ikb)}{2b}\right)=2\pi\exp(-ka)\frac{\sin(kb)}b\;.$$
If $k\le0$, you can complete the integral by a half circle at infinity in the lower half-plane, since the integrand decays quadratically (or exponentially for $k\lt0$) and the perimeter of the half circle increases linearly. There are no poles in the lower half-plane, so in this case the integral is zero.
Comment: Remains the case $b=0$.
Comment: Basically the same remark as for Ali's answer. If $k<0$ the contour should be closed in the lower half-plane and the integral will be zero.
Comment: @Heike: You're right of course; I confused $a\gt0$ with $k\gt0$; I'll edit the answer accordingly.
Answer: Assume $b \neq 0$ and $k\neq 0$.
Write
 $\dfrac{\exp(ixk)}{-x^2+2iax+a^2+b^2}= \dfrac{\exp(ixk)}{-(x-ia)^2+b^2}=\dfrac{\exp(i(x-ia)k)}{-(x-ia)^2+b^2} \exp(-ak)$ hence
the integral becomes $I=\int_{-\infty}^\infty \dfrac{\exp(i(x-ia)k)}{-(x-ia)^2+b^2} \exp(-ak)dx=\int_{-\infty-ia}^{\infty -ia} \dfrac{\exp(izk)}{-z^2+b^2} \exp(-ak)dz$ on the contour the straight line parallel the $x$-axis and intercepting the $y$-axis (imaginary) at $-ia$.
 We need to close the contour by a great semicircle in the upper half plane if $k>0$ and in this case there are two poles at $z=b$ and $z=-b$ enclosed in the contour.
Now we will use the residue theorem. The poles of the fraction $\dfrac{\exp(izk)}{-z^2+b^2}$ are $-b,+b$ and then the integral will be $I=(2\pi i)\exp(-ak)\lbrace Res(z=b)\exp(ibk)+Res(z=-b)\exp(-ibk)\rbrace$.
 Now observe that $Res(z=b)=1/2b$ and $Res(z=-b)=-1/2b$ hence $I=2 \pi i \exp(-ak) \frac{\sin bk}{b}$.
 If $k<0$ then we close the contour by a semicircle in the lower halfplane and in this case there are no poles enclosed and so the integral becomes zero.
Now assume $b=0$ and $K\neq 0$: in this case the residue (at $z=0$) becomes $-ik$ and the integral becomes $2\pi k$ (if $k>0$) and $0$ if $k<0$.
Finally let $k=0$: then in this case the result will be easy and I leave it for you as an exersice.
Comment: Remains the case $b=0$.
Comment: you have to be careful to close the contour in the right half-plane. Since $\exp(izk)$ blows up for $Re(izk)\rightarrow\infty$ and goes to zero for $Re(izk)\rightarrow-\infty$, you should close the contour in the upper half-plane for $k>0$ and in the lower half-plane for $k<0$. Depending on the sign of $k$ you'll have either 0 or 2 poles inside the closed contour.
Comment: Thanks for your remarks. I will make the necessary changes later tonight.


Making a sound that's loopable.

Question: I want to make a rocket 'whooooooooooooooooooosh' sound that can go on FOREVER. I have the sound I like, I just need some protips on making it loop. I've been hacking away at it in Pro Tools, and when I loop it in there, it works, but when I implement it in the game I'm working on, there's a clear loop point. Any idea how I could remedy this? I also saw the Rabbit Ears Audio rocket pack, which would be like, perfect for what I'm doing. If you were taking a sound from a library, what would you do to it to make it something that could loop?
Answer: Try it in game.  You probably won't notice the loop as it's flying by you.  If you do, take that same sample and offset it in another track in Pro Tools.  Bounce that down and loop that.  That should help remedy it.
If that's really not solving the issue then look for another static track to layer in.  Jet airplanes are good for rocket bys.
Be sure that your loop point is at the zero crossing as well.  If you game dynamically pitches it (with doppler effects) or you pitch it in game you could induce a pop/click in the loop as well.
Answer: hmm... maybe there's a way to combine it with a Shepard tone so the doppler is "continuous"  (assuming our perspective is fixed from outside the rocket)
http://en.wikipedia.org/wiki/Shepard_tone
Comment: Is that some sort of a barber shop pole for audio?
Comment: Essentially, yes. You can easily generate them with a plugin from the mda au/vst collection - http://mda.smartelectronix.com/
Answer: if you are into the game industry, check the spec of the audio engine. if you are more into the post production area, check AKAI sampler or Kontakt might be useful. I have successfully use a sound of a food processor to create a sustaining rocket-interior kind of sound using an Akai sampler (S-1000)
Answer: surely the way is to seperate construction of the events
the doppler effect is most noticeable when it passes the listener,
so from launch, to close passby, to close away use Michaels awesome rocket sound
then

make the constant rocket engine sound
(like you have a mic gaffer-taped to the side of the rocket)
apply the doppler via a very long/slow LFO'd filter of the constant rocket sound!
it would take some matching.... and some epic verb!
but who is going to check that it actually goes on FOREVER?
(could you ask them to also check my perpetual motion machine while they are at it?)
Answer: This may sound simplistic but I'll be glad to share what I've learned from a recent game project earlier this year. Make sure you have clean heads and tails. You may be able to loop well in Pro tools because of the region you selected. But when you play the wav file completely, you may still have some audio at the start and at the end that could and should be trimmed off for a clean loop.
Also, if you're using it for a game and space is an issue then the problem may occur when converting from Wav to MP3 file. If you're broke, like me, then you might not have the DV toolkit yet which allows you to bounce mp3 files. Recently, I used a program/media player called VLC to convert a wav file to mp3.  But for some reason, VLC doesn't make a clean conversion, there's always some extra audio at the end and/or beginning of the file. Your best bet then is to use the free program, Audacity, to do your wav to mp3 conversions. Your MP3 files will come out with no extra filler added that would make a clean loop impossible.
Comment: Be careful using the Digidesign/Avid mp3 option. I was at an AES convention last year listening to George Massenberg talk about mp3 encoding. He talked about a test that was conducted to see which created the cleanest encoded file (fewer artifacts, etc.), and the mp3 bounce option for Pro Tools came out dead last.  The one built into Apple's iTunes proved to actually be one of the best, which surprised me.  I wish I remembered which others he mentioned as being a good choice.
Comment: As far as I am aware, due to the nature of MP3 encoding/decoding there will always be a short silence at the beginning and end of a file, regardless of whether it is bounced directly out of Pro Tools, or encoded later on.
Comment: @Shaun_Farley Wow, that's amazing. Not that i would have assumed it to be the best. But to be the worst?! that's crazy...Frankly, for a really expensive program that's a bit of a shame. Especially since Logic has the ability to import OMF files as a standard option. A thousand dollar program should not be coming in last. What a shame
Comment: @James_Bryant I would not argue against that at all. But Audacity appeared to create the perfect loopable sound files for me.
Comment: @Malvicus lol. Yeah, Massenberg said almost the same exact thing, but (in Pro Tools' defense) that was really the only thing he discussed as disliking in it. He still uses it for everything else, and just turns to iTunes when he needs to make a compressed audio file.

Making a sound that's loopable.


Webcam image as desktop wallpaper in Windows 7?

Question: Is there a way to set the Windows 7 desktop wallpaper to an image from a live webcam feed?
Answer: In Windows 7, the Active Desktop feature -- which allowed you to set HTML content as your desktop -- has been disabled, so your options are limited.
One method is to set your background to point to a particular directory, and then set the "Change picture every" interval to the minimum of 10 seconds.  Then you can use a piece of time lapse software to dump image captures into the folder at regular intervals; Windows watches the directory you set so it will automatically find new images dumped there, and incorporate them into the slideshow.  Open source options include chronolapse (for a local webcam) and livedesktop (for a URL-based webcam).
Setting whatever software you use to assign progressive filenames to the images (like timestamps) will ensure that Windows steps through the images in order and does not display old ones; be sure to un-check the "Shuffle" box.  You will have to either manually clean out the image dump folder from time to time (or write a script to do so) to ensure that it does not balloon in size if the time lapse software is run for an extended period of time.
Another, more "live" method is to stream the webcam output (from a local webcam or a remote one) to VLC media player and then have VLC play the video directly on the desktop (Video --> Set as Wallpaper).
Answer: Are you talking about having a live feed automatically display as the wallpaper?  I found this: http://www.wallpapercam.com/ however I have not used it and don't know about it at all.  It appears to be subscription/purchase software.  Hopefully this helps with that.
Otherwise by right clicking on the desktop, selecting personalize and then Desktop Background you can select any picture on the PC.
Comment: Yeah, I'm talking about a live feed.
Answer: Webcam Wallpaper allows to fetch the image from URL every X minutes and optionally stretch it to the desktop:
Answer: There are some third party products enabling this, see http://www.google.com/#q=webcam+wallpaper


What is the biggest component difference between a cheap road bike and an expensive road bike?

Question: I am shopping around for road bikes now, and I wanted to know what components to look for. I am not talking about the frame, carbon or otherwise, I mean types of shifters, brakes, cranks, rims, etc.
Comment: Sounds like you're new to buying expensive bikes-  Do yourself a favor and buy from a local bike shop (LBS).  You will need them to stay in business.  After you already know the answer to your question, then you can strike out on your own and buy something on the internet.
Answer: As with any other equipment, it depends on how much you would like to spend...
The main difference between a cheap and a better bike is the quality of the materials and the comfort/performance they provide!
I have several cheap bikes and two "better" bikes, the differences between these are:

better derailleur system, both the front and back, it makes a lot of difference!
better shifter (the cheap one has a thumb-type shifter, and the better has a shimano trigger-type shifter), for me having trigger-type shifter is a huge difference in comfort
better brakes (you could go for the v-brakes, but there are some flavors to choose from; you could also go for a disc-brake; also the brake levers can make a lot of difference also!)
tyres, normally the cheap bikes have sub-par tyres and tubes.
obviously the wheel (good rims, good spokes, I have noticed that indeed!)
the frame, weight, strength, shape (cheap frames can affect a lot on the way you ride, but honestly I've had cheap frames and loved them!)
seat, a good seat and seat post are important.
overall, good materials, that don't disintegrate after some time and resist (as possible) to the corrosion.

I may have forgotten something but this gives you an idea.
Comment: what makes the difference in the derailleur system?  You claim that there is a difference however you have not really told us what it is.  Could you offer more explanation?
Comment: @sixtyfootersdude from my experience, the derailleurs that come with a cheap bike are very weak (material-wise) and not very accurate (you can skip cogs), not to mention that probably aren't destined to trigger-shifters, at least the cheap ones I have. A *better* derailleur will have a more accurate shifting function I can vouch on this one, I have both cheap and better bikes and am in the process of swapping some components and the derailleur will be one to swap. Mind you that I see some advantages in a thumb shifter but IMO the derailleur can be the key, even for this shifter type.
Comment: Cheap bikes often come with cranks that have the chainrings welded on to the crank arms, and cannot be replaced without replacing the entire crankset and possibly the bottom bracket as well.  Often these cheap cranks are made of steel instead of aluminium alloy due to the cheaper cost of those lines.  Steel is usually not as desirable for this purpose on higher end bikes due to the extra weight vs aluminum.
Comment: Note that lower spokes is also not necessarily a good thing. High end wheels with low spokes are typically built better than lower end ones (which may end up weighing more than a wheel with more spokes) and be less durable.
Comment: @sixtyfootersdude aditionally, the cheap derailleurs that I have and that may come with the cheap bikes, can (mine do) have a poorer fine tuning mechanism, for instance, the cable can't be "tuned" at the derailleur's end, or the high + low callibration is in such a place that I can hardly see what I'm doing, also the springs are very bad.
Answer: After the frame, wheels are the second most important element of a bicycle. Wheels are also the second most expensive and at times even more expensive than the actual frame. In terms of advice on buying a bike, start with your budget and back into the best frame, wheels then components money can buy. Another strategy some guys use is to buy the bike with the best frame/gruppo combo possible, then know they will upgrade wheels when $$ begin to flow again in a few months. I have used both of these strategies successfully, but now prefer the first as most components are very good...but that is not true of all wheel sets.
Off the cuff, without an overly detailed answer, cheap versus expensive can be summed up in 4 words: comfort, efficiency, weight and durability.
If you give me an idea of what type of riding you are looking to do and how much you are looking to spend, I will gladly provide some decent steeds to take a look at. Or if you look at a couple of models and want some feedback, I am sure you will get lots of responses if you post again here!
Good luck!
Answer: manufacturers of bike components (there aren't that many) universally put up their line in "groups".
These go from the cheapest, which often have no name at all, to the most expensive.
Shimano's top-of-the-line for road bikes is "Dura-Ace", for instance.  With "Ultegra" below that, and then "105", and so on.
Better components are lighter, often rebuildable, and usually operate in a very "slick" manner.
Often the difference is hardly perceptible... And in some cases the "better" components are also more complicated and more likely to be in need of constant adjustment.
Comment: True as far as it goes. In my experience, however, higher end components are rarely more in need of adjustment compared to more basic components. Although often their owners are more in tune with what out of adjustment feels like, and are often maniacal about wanting perfection. So it may feel like that is true. Myself included :).
Comment: I haven't actively compared components for about 20 years, but back then one problem was that component manufacturers produced a dozen different models of essentially the same thing -- often a different one for each bike manufacturer.  This prevented you from doing an "apples-to-apples" comparison of bike componentry, since you never quite knew if two different models of, say, a derailer were really substantially different in quality or only different in model number and perhaps finish.  This has apparently changed a little since Shimano gained a monopoly, but I don't know how much.
Answer: A good derailleur will change smoothly while under heavy load, i.e. while you are still pedaling.
They will also be capable of upgrading or changing the cassette, (the bundle of cogs at the rear) for different gear ratios and will have more options to do so.
The same applies to the crank-set i.e the 2 or three big cogs at the pedal end.
Answer: New road bikes are generally available from two sources: your local bike store (LBS) and online. Not all brands are available from both types of distribution channel. That makes it harder to compare apples to apples.
Too, your LBS/brick & mortar retailer probably has a clearance sale starting sometime around August to clear out inventory and make space for next year's models. If you want to compare apples to apples, keep that in mind. You can get some very good deals in this way, which can be hard to beat online. The online-only sellers almost never have any kind of substantial sale.
In light of that, let's look at a couple of examples:

Lynskey Helix with full Ultegra drivetrain ($4950 assembled)
BikesDirect Motobecane Le Champion with full Ultegra drivetrain ($2100 assembled)

These bikes are very comparable in many respects. Both have a titanium frame, but the Lynskey frame is made in the USA, whereas the Motobecane frame is made in Taiwan. The Lynskey frame has a certain cachet among cyclists which the Motobecane frame does not have. If you were to compare the two frames side-by-side, you may find that the welds on the Lynskey are slightly prettier than the welds on the Motobecane. (The frame builders at Lynskey might be using multiple layers of weldment to help achieve that.) The other components are pretty comparable; I own and have ridden many miles on both the Aksium and Equipe wheels, for example, and there isn't much difference. The fork on the Lynskey is nicer and more expensive, but apart from that, all the components are entirely comparable in terms of price and quality. You can read online reviews of both bikes, and they both review favorably. The price for the Lynskey, however, is $2850 more.
This is sort of an apples-to-apples comparison, in that both bikes are available online and you can get them through certain dealers.
Take another trio of road bikes and compare:

Trek Madone 4.7 with a mostly-Ultegra drivetrain ($3150 MSRP)

Specialized Tarmac SL3 Expert with a mostly-Ultegra drivetrain ($3900 MSRP)

Motobecane Immortal Force with a mostly-Ultegra drivetrain ($1600 MSRP)

Look at the specs for each of these; you have nicer wheels on the Specialized, and there are other differences. But all the frames are made in Taiwan, so far as I know. A big part in the price difference comes from paying for the distribution channel. The dealer has to make a profit to stay in business. Trek & Specialized are mainly distributed through brick & mortar retailers; BikesDirect has some brick & mortar retailer distribution, but mainly they sell online.
Full disclosure: I ride a Motobecane Le Champion with the titanium frame; I have about 4100 miles on the bike, and I'm totally happy with it. I also have a Trek Fuel EX 8 that I scored on clearance from a brick & mortar retailer. So I have no problem to buy either way.
Bottom line, you have to decide how much you are willing to pay for brand name cachet and LBS support. But I think it is fair to conclude that the dealer-centric brands cost more.
Comment: LBS support is a big deal for most people - sizing a bike from just measurements is difficult, especially for people who haven't owned multiple bikes before.
Answer: There is a big difference in component quality, for example I have a bike equipped with Ultegra and another bike that has mixed Sora and Tiagra groupset. As mentioned above Shimano Ultegra is fairly expensive while Shimano Tiagra and Sora are near the bottom of the range.
The cheaper Sora/Tiagra groupset requires constant attention, the shifters and the brakes feel spongy to the extent that I replaced the brakes with Ultegra after a few months as the Sora brakes felt unsafe. This did not entirely cure the problem as the main culprit are the shifters/brake levers. Replacing them is very expensive.
The Ultegra components are stiffer as they use better materials. They last for years and do not corrode as much as their cheaper cousins.
It does depend on usage, racing cyclists buy top of the range components because they are light and perform well even under maximum load and stress. If you are a weekend warrior that likes to potter around and do not need ultra-efficient brakes to get yourself out of trouble then go for the lower end components.
Comment: You are forgetting the third segment of the biking population: the commuters. People who bike every day not to go fast or for exercise primarily, but to get from point a to point b. What do they want? Quality? Durability? Cost efficiency? The answer is all of the above. I find buying components for my daily commute is the hardest.
Comment: True, I have a Dawes commuter bike that is 14 years old which has very basic bottom of the range shimano. It mostly works fine with very little attention. Mind you my daily commute is two miles to the railway station.
Comment: Last time I built up a cyclocross bike for myself I used Dura-ace shifters driving a Tiagra front derailleur and an LX rear derailleur. Oh, and Ultegra cranks
Answer: Just go for the cheapest derailleur you can buy. They all have a big spring, two jockey wheels and a cantilever system. Both expensive and cheap ones wear out at about the same rate.
They both get gummed up with crud.
When new, they shift identically... why wouldn't they?. When really worn out, the jockey wheels wobble and shifting isn't so precise.
Maybe the few, very expensive derailleurs with jockey wheels that use bearings may last a little longer (perhaps they don't, perhaps they're pointless) ... but why pay 4x for this benefit?
Forget all this nonsense about "better quality material, better made" - and no-one being able to tell you what specifically is better. It's all marketing rubbish for gullible consumers.
Comment: The fact that people will currently buy a derailleur if Shimano says it is better,pretty much on faith in what they say, is based on 50 years of experience with Shimano's products and finding that what they say is truth. That reputation is only 2 generations of product from failure at any given time. If the next generation comes out and they say it's the best of the best, and it isn't, then at least the majority of people will not buy the generation after. I strongly disagree with this answer, and also with the comments by @DanielRHicks, obviously.
Comment: If I am understanding you correctly I am going to have to disagree with you. If there was no difference in components on a bicycle then a WalMart bike would be of the same quality as one at a bike store.
Comment: There are some sheep that will buy whatever they're told, but they aren't the majority. And good products aren't made for them. They are the idiots that buy knock offs and say it's all about the label. They forget that the label had to have a quality, and a reputation first, for the label to be worth anything at all.
Comment: I think *user's* point is that you can't tell what the difference might be, even if you read all the marketing literature and reviews.  Is component B really better than component A from the same manufacturer, or is it just a different color coat of paint.  Remember that there's a big advantage for the mfgr to use the same design, the same dies, etc, for making several different models.
Comment: There may be a difference in the metallurgy or in the finish, but there may not be -- If Shimano slaps a new "Ultra-Super-Duper-Sexy" label on a component and jacks up the price 30% there will be some number of people who buy it, and Shimano will have more money in their pocket for essentially zero effort.
Comment: @zenbike - there is such a thing as a "Brand Whore", and in some industries, it is prevalent and the manufacturers take advantage if it to maximize profit.  In the case of bicycle components, I think you are right - you get what you pay for, however, I would go as far to say many riders fit better than they need just so they can say that have it.  How many who think 50km is a big ride insist that 105 is not good enough?
Comment: @mattnz: There are, as I stated, people who buy for looks or bragging rights. Just like there are people who line up outside the Apple store, a week in advance of the release of a new iPhone. But if the iPhone 5 comes out, and is a crap phone, the brand will lose the drawing power for even these people. And if 2 in a row come out that way, the brand will die, unless the do something spectacular to make up for it. The fact that some people don't need Dura Ace, does not mean there is no difference between Dura Ace and Tiagra, or even Dura Ace and Ultegra.
Comment: Choosing to buy more than you need is between a person and their wallet.  I will never need Dura Ace from a performance perspective, much less the electronic version. But I can afford it, so why not?  I don't ever tell someone, "you need this". Lets be real, a bike will ride on Tiagra or 105, just fine. It's not going to break down or stop working. And you can drive a VW Golf, just fine too. You don't need the GTi.  But they are not the same product or performance and if you can afford the nicer car and appreciate its performance or its luxury, why not?


How can we determine when an image is a symbol?

Question: Put simply, a symbol is a tangible representation of an intangible idea.  Authors, both ancient and modern, use symbolic images to convey abstract concepts.  The problem with symbols, however, is that they often appear as part of an implicit communication between author and audience. It's thus possible to misread an image as a symbol or a symbol as simply an image.  Are there criteria to aid readers in determining when biblical authors use images symbolically?
Comment: Matt, could you possibly provide an example of what sorts of passages you are wondering about? With the ambiguity in terms and variety in perspectives out there today it is tough to know exactly what you are seeking based solely on linguistic descriptions. Is there a particular passage that has caught your attention in this regard? If not, could you give us a couple of examples of each to clarify your question?
Comment: Here's an example.  Is it possible to determine more or less objectively that the author of Jonah intended his audience to see Jonah as symbol for the nation of Israel?  Note that symbolism does not necessarily rule out an individual or event being also historical.
Comment: Actually I planned to answer this question myself.  But I haven't got around to finishing it.  I brought it up because I think my appeal to symbolism here  ( http://hermeneutics.stackexchange.com/a/4872/2230 ) may have been a bridge to far for some.
Answer: Here are a few things that might help point the interpreter in the right direction. (NOTE: This answer is from a Christian perspective)
The referential nature of language
Language is referential. If I say "I own a house," any English-speaker will recognize that I am referring to a place of residence. However, if I said "I own a lamaroutous" that would be nonsensical, because that word does not currently refer to anything under the modern conventions of the English language. My audience would have no hope of understanding my speech. When we speak, we have to use words that are known to our intended audience.
Referential language works fine for day-to-day life in this world; I can "arise" from my "bed" and "eat" some "cereal" before I "read" the "newspaper"... and I can communicate that to virtually any English-speaker without a problem.
The purpose of a symbol
Communication is more difficult when you are attempting to describe something unfamiliar. For instance, when God attempts to describe future and/or spiritual realities to a local audience that is neither future nor spiritual, it becomes necessary to speak in familiar terms while describing the unfamiliar. This is where symbols come in. A symbol allows you to refer to something unfamiliar by way of a familiar term.
For example, God promised to send "Elijah" before the Day of the Lord. Jesus identified John the Baptist as the Elijah who was to come. If the prophecy had said that God would send "John the Baptist" that would be nonsensical, since no one would have had any idea what that term referred to! By saying "Elijah," God is able to call to mind something familiar which could give the audience a sense of what kind of person to expect.
So, start by examining the passage to determine whether the speaker is intending to communicate something unfamiliar (e.g. future or spiritual) in familiar terms.
Genre
In general, properly identifying the genre of Biblical literature is crucial to interpreting it correctly. Just as we must be careful not to confuse a comic strip with a news headline in the local newspaper, we must be cautious of confusing apocalyptic literature with historical narrative, or parable with discourse (etc.)
This is helpful for identifying symbols, because symbolism is much more common in some genres than others. For example, apocalyptic revelation typically comes in the form of dreams and visions, which tend to be highly symbolic, versus historical narrative, which is almost never communicated through symbols. (Although the events themselves may have been divinely intended as "symbolic"!)
God's focus is spiritual
This may perhaps make more sense to Christian interpreters than Jewish or secular, but God's ultimate concern is for the redemption of mankind, and that is a spiritual redemption. It was never really about moving a group of blood relatives to a new geographical location and helping them slay the other people around them. God's heart was never in slaughtering animals, or throwing rocks at sinners.
God's heart has always been for the redemption of mankind. His mission is to restore mankind to relationship with Himself. Ultimately, everything God says and does serves this purpose. Thus, anytime we see God speaking about something natural and temporal (i.e. non-eschatological) we should suspect that it is symbolic. And anytime we see God doing something natural and temporal, we should suspect that it is typological (which could also be called "symbolic.")
Jonah, for example
In order to confidently identify an image as a symbol, we must be able to show that the author (or Author) intended it as such. This can be as simple as showing from the text that the human author was using a metaphor. For example, in the opening chapter of John the narrator writes:

"In the beginning was the Word . . . All things came into being through Him . . . In Him was life, and the life was the Light of men. The Light shines in the darkness . . . ." -John 1:1-5

Here we can clearly see John using "Light" as a metaphor (a symbol) of the Son of God.
Since we are here wondering whether Jonah himself is symbolic, or whether the story as a whole is a spiritual commentary, we could also explore the possibility that God meant His sovereign actions there as symbolic -- just as God used the Exodus symbolically to teach us spiritual realities.
Again, given God's agenda, this is highly likely. The alternative -- that it is merely an ancient story of a repentant country and a prophet with a bad attitude -- is more difficult to sustain. It probably is "symbolic" in some sense.
This does not suggest that the story of Jonah is not true, or historically accurate -- it merely suggests that what God did there pointed to something future and spiritual. It pointed to God's ultimate concern: the redemption of mankind.
Answer: Rabbi Samson Raphael Hirsch dedicated many essays to this subject. They may be found in English translation in his Collected Writings, Volume III; ISBN:0-87306-786-X.
The primary tools Rabbi Hirsch uses in his analysis are the following ground rules, which he develops in the introductory chapter (slightly abridged for convenience):

The symbolic significance of an object or act is never intrinsic but always derives from the intentions of the one who instituted that object or act as a symbol. Symbols are intentional, or they aren't symbols.
When assigning a symbolic role to an object or act, several of its aspects (e.g., natural, social, historical) must be taken into consideration.
The symbolic meaning of an object or act depends

on the presumed intention of whoever instituted the that object or act as a symbol,
on the ideology presumed for the addressee of the symbol's message, and
on the historical and local identification of the symbolic object or act.

These aspects must therefore be taken into consideration when seeking to establish the symbolic role of any object or act; particularly its connections to its originator and its addressee.
Symbols can never reveal ideas or facts that were unknown before. Symbols can only demonstrate new relationships between known ideas & facts and thus serve to commit these ideas & facts to memory.

Taking the OP's example question "[Might] the author of Jonah [have] intended his audience to see Jonah as symbol for the nation of Israel?", we can submit it to Rabbi Hirsch's criteria:

There is no requirement that a prophet represents, a priori, the nation of Israel; by asking about the intention of the Book's author, the OP is on the right track.
In what way does the character of Jonah, or his actions, or the way the author speaks about him, indicate that he might serve as a symbol at all? Does any part of the story contradict the symbolic interpretation? (For example, you don't get to ignore the story of the gourd plant when building up a picture based on the earlier parts of the story.)
In what way would this story have been taken as a symbol by its audience? (An interpretation of Jonah relating the story to the establishment of the modern State of Israel would be a nice eisegesis, but could not be taken seriously as the symbolic meaning of the Book. The symbol's meaning may be lost and rediscovered, but must always have been valid.)
Is the lesson you're drawing from this symbolic interpretation a new idea (an invalid use of symbolism), or is it teaching a lesson by emphasizing a previously-known point or connecting known ideas?

This analysis doesn't rule out every possible interpretation of "Jonah as a metaphor for Israel" (though it leads me to doubt one can successfully be constructed), but it is a powerful tool for checking any such proposal.
Comment: As an aside, rule #3 would tend to exclude most Christological readings of the Hebrew Bible ["Old Testament"]; Rabbi Hirsch would consider this a feature of his system, not a flaw.
Comment: @MatthewMiller, I didn't think you'd meant that; I used that as an example of a clearly invalid reading.
Comment: +1 Thank you very much.  Great answer!  I should have been more specific in asking if Jonah was meant to be a symbol for the historic nation of Israel, pertaining to the time in which Jonah was written, and not the modern state.
Answer: As is the nature of historical fields, such as the anthropological and linguistic fields which serve as our surest means of understanding such colloquial forms of language, at least some uncertainty or ambiguity will always haunt our attempts at determining the meaning of symbols, or most any other metaphor for that matter. Rationally speaking, it is a matter of continuing to uncover and learn the ancient contexts, psychologies, and uses of languages. But there is also a means of understanding some symbols by less rational (though not therefore irrational: merely arational) sources of knowledge, such as artistic perceptions like the sense of the aesthetic, of the narrative, of the intuitive and empathic, etc. And of course it is also a matter of spiritual discernment and prayer, which is unfortunately not so often emphasized in theology and hermeneutics as one would expect. Christian academic subjects they may be, but Christian they must remain!
In short, there is no easy answer. This, like so many other linguistic difficulties in Biblical hermeneutics, are a matter of diligence, of skill, of art, of happenstance (or providence, as it may be), and perhaps even of revelation.
NOTE: This answer was written in response to the original form of the Question, which appeared to me to be seeking a definitive rule by which to identify symbols with certainty. I have edited this Answer to align a little more closely with the now-edited Question, but in deference to the original purpose of this Answer and to avoid redundancy, I will leave to others to address the exegetical concern, as Jas 3.1 has done so well already.
Comment: I agree that 100% certainty in communication is impossible and that language is in part subjective. But I wouldn't therefore conclude that there is "no, and could be no, such objective means of determining" someones meaning.  Communication involves both senders and receivers and therefore it is both objective and subjective.  The objective sender places limits on meaning while the subjective receiver attempts to faithfully interpret meaning within those objective limits.  This is precisely why its important to carefully define our terms.  Symbols like words are defined by culture or text.
Comment: How can "continuing to uncover and learn the ancient contexts, psychologies and uses of language" have any bearing on the meaning of symbols if they are "fundamentally subjective?" Its seems to me your too broadly defining subjectivity as anything less than 100% percent certainty.
Comment: All language is fundamentally subjective. That absolutely means 100% certainty in communication is impossible. We only communicate inasmuch as my definition of a word or phrase aligns to yours. Symbols are even less certain due to frequent colloquial nature. This is why, for example, many arguments relying the term "free will" result in debate or confusion: different groups define it differently, and thus clarifications should precipitate discussions on it. The difficulty is attempting such clarification with millenia-old texts between alien cultures and wildly heterogeneous contexts.
Comment: If communication is both objective and subjective because it involves both senders and receivers, then we are working from different understandings of objectivity and subjectivity. For reference, I am using those terms in a Kierkegaardian sense, and so I cannot say that senders are objective. Certainly in the Humean sense, too, they are not, nor can be! But anyway, we're on the far outlying regions of relevance to the OP.
Comment: Got it.  In the OQ I'm using the term "objectively" in the sense that its commonly used, "not influenced by personal (subjective) feelings or opinions in considering and representing facts."  Being objective is to base ones conclusions on evidence observable to others.  Senders and their messages are objective in the sense that they exist outside the subjectivity of the receiver/interpreter.  That aside, Welcome to Biblical Hermeneutics!
Comment: Great answer. I understood your usage of "subjective," but as you noted in your comment about "free will," the term carries different connotations depending on usage. Since the OP was using the terms differently, it would be helpful to clarify how you are using the terms, or stick with the vocabulary he was using. Thanks for the great contribution though. Please continue to share your insight!
Comment: @GoneQuiet Sure.  "Are there criteria to aid readers in determining when an a biblical author uses an image symbolically?"  I hope that helps.
Answer: If an author intends to communicate through symbols he must either rely upon a community's preexisting symbolic language or make an effort to define the meaning of the image within the text itself.  Ruben Zimmermann in his book Imagery in the Gospel of John thus offers two criteria for weighing a symbols plausibility: (1) conventional plausibility and (2) textual plausibility. He returns to these two criteria in Anatomies of Narrative Criticism

With regard to the criterion of convention plausibility, if a motif
  such as "light," "shepherd," and the like holds a great deal of
  religious meaning within a linguistic community due to a
  Bildfeldtradition (traditional semantic field) that can be
  substantiated by means of older and contemporary texts, then there
  exists a high level of plausibility that the motif is being used
  symbolically, in line with conventional usage.  Here we may speak of
  evidence of plausibility outside the text. The criterion of textual plausibility would hold that the way in which
  an author identifies a motif within a text as a symbol will be made
  clear by clues in the text.  Thus I would speak here of evidence for
  plausibility within the text.  The symbolism of a text can be
  identified from the specific interaction between social-traditional
  convention and the actual textual-evidence.

When an author appeals to convention by assuming his audience will recognize his meaning he or she draws a curtain between his group and those outside his community.  The only way for present day outsiders to peek behind this curtain is to acquaint themselves with the common sources from which this community derived its symbols.  For instance, John's symbolic language like the Greek language he speaks arises in part from his social setting.  Giving heed to the material that evidently played a part in his writing can supply ample information for symbolic investigation.  Thankfully, with regards to the religious books of the Bible, their sacred texts are by and large still with us today.  The plausibility of a proposed symbol is thus first weighed by its continuity with known scriptural convention.
But authors also define their symbols within the text.  This occurs in at least two ways.  First the author can use the narrator or characters within the story to make an explicit connection or comparison between two unlike things. A good modern example of how this shift takes place can be found in the movie The Shawshank Redemption.  Notice how Andy links music to hope and Red more specifically to a harmonica.

ANDY: (taps his heart, his head) The music was here...and here. That's
  the one thing they can't confiscate, not ever. That's the beauty of
  it. Haven't you ever felt that way about music, Red?
RED: Played a mean harmonica as a younger man. Lost my taste for it.
  Didn't make much sense in here.
ANDY: Here's where it makes most sense.  We need it so we don't forget.
RED: Forget?
ANDY: That there are things in this world not carved out of gray
  stone. That there's a place inside of us they can never lock away, and
  that place is called hope.

Later in the film the mere image of a harmonica becomes a symbol by invoking the metaphor of the previous conversation.  Andy gives Red a harmonica as a "parole rejection" present.  When asked if he's going to play it, Red responds, "no, not right now."  The gift has moved beyond a mere object and now points to the hope which Andy provides and Red doesn't want to let in.
In John's gospel the symbols most easily recognizable are those found first in metaphor.  "I am the light of the world" Jesus says.  The incongruity of Jesus speaking of one thing in terms of another pushes the reader passed a literal meaning to reconcile meaning abstractly.   Metaphors clearly denote John's core symbols, images that occur frequently and contribute most to the gospel's message.  For instance Christ's claim to be "the light of the world" establishes light as a symbol.  Its frequency and placement underscore its vital importance (1:9; 3:19; 8:12; 9:5; 12:46).
A second way an author can define a symbol is through narrative structure. For instance, Mark, the earliest of the four New Testament gospels, records the following scenes in this order.

Jesus looks for fruit on a fig tree but finding none curses it (11:12-14
Jesus enters Jerusalem and attacks the temple (11:15-19)
The disciples see the fig tree withered from the root and ask Jesus about it (11:20-25)

The sandwiching of these stories indicates that the fig tree is a symbol of the temple. The cursing of the fig tree and its subsequent withering represents Jesus attack on the temple and its subsequent destruction.  Jesus' later teaching on the mount of Olives (Matthew 24, Mark 13, Luke 21) has this meaning in mind.  Here, Jesus appeals to the meaning of the fig tree.

Now learn this lesson from the fig tree: As soon as its twigs get
  tender and its leaves come out, you know that summer is near.  Even
  so, when you see these things happening, you know that it is near,
  right at the door.  I tell you the truth, this generation will not
  pass away until all these things have happened.  Heaven and earth,
  will pass away, but my words will never pass away.

One further thought.  The symbols arising from the original metaphor or structural association need not be restricted to their specific language.  For instance if Red had never made the explicit connection between music and a harmonica the harmonica still would have been a plausible symbol for hope in the proceeding scene.  That's because a harmonica is a subset of the larger concept of music.  For example, later in the Shawshank Redemption, we find Heywood listening to Hank William's records in the Library Andy has built.  While Hank Williams has not been explicitly connected to the metaphor his music falls under the same category.
This occurs repeatedly in John's gospel.  Beyond metaphors to light we find linked references to things like darkness, day, night, blindness, and sight.  The conceptual link to a central symbolic image suggests that these images likewise are to be understood symbolically.  Philip Wheelwright has observed that many symbols have "a bright focused center of meaning together with a penumbra of vagueness that is intrinsically ineradicable."  The core symbol established in metaphor and clearly defined in context acts as the "bright focused center" while the linked images appear to radiate out in more or less decreasing precision.
Some of these images are more transparently symbolic than others.  For instance, when the statement "men loved darkness rather than light" appears at the end of Jesus' dialogue with Nicodemus it suggests that Nicodemus' approach by "night," is more than simply setting.  Likewise the regular reoccurrence of light in John indicates a similar symbolic sense for Judas' final departure (13:30) though only "night" is mentioned in the immediate context.
Of course not all images related to a core symbol have this probability.  Craig Koester states,

When attempting to identify elements that may function symbolically as
  part of a motif, we do well to say that some are almost certainly
  symbolic and that others are only possibly symbolic.

Frequency and or context are once again the clearest guides to establishing likelihood.  For instance, John's light motif may play an ironic role in the solder's use of lanterns and torches to arrest Jesus, "the light of the world."  However, because lanterns and torches are not mentioned or connected elsewhere in John with the light motif, the probability of an intended symbol, though good, is not as great.
Comment: Some good thoughts. I would challenge the fig tree example though, [on this basis](http://christianity.stackexchange.com/a/7221/1548). With the light motif, Jesus identified Himself as the light of the world in a particular context for a particular purpose. John shared portions of Jesus' discourse for a particular purpose, but that does not mean that *John* was establishing a symbol for his own use outside of Jesus' discourse.
Comment: @Jas3.1 I really appreciate the feedback. Can I ask for more clarification? I read your answer but I'm not sure on what basis you are challenging the fig tree example. I realize Jesus spoke in a living context but his meaning is mediated for us today through a narrative world which have been artificially created by the Evangelists. They redacted history (choosing to include or exclude what they new) to interpret history just as all historians do.  I have attempted to show how John draws symbols from Jesus' spoken words. Why do you think he isn'?  How would you interpret John 4:28?
Comment: RE: the fig tree, Mark may have been implying a similarity between the fruitless fig tree and the temple, but I am wary of "the fig tree is a symbol for the temple" given the typical usage of the statement. RE: Redaction, I agree. RE: Jesus' symbols, they are His, not John's. It has to be shown that John was *also* intentionally establishing a symbol (vs. intentionally including the discourse for another reason.) RE: John 4:28, she left in haste. I think we need to be cautious of drawing too much significance from a single word. (I would suggest posting a separate question for this one.)
Comment: Would you explain how I can show that "John was also intentionally establishing a symbol (vs. intentionally including the discourse for another reason)?" I really thought that's what I was doing in my answer.
Comment: In John 1:1-5 the narrator explains "In the beginning was the Word . . . All things came into being through Him . . . In Him was life, and the life was the **Light** of men. The **Light** shines in the darkness . . . ." Given the context and the genre, it is easy to see here that the narrator is establishing a symbol by speaking metaphorically about the Son as "the Light." However, I don't think it is safe to assume that because John recorded a discourse which includes Jesus establishing a symbol that the symbol carries over outside of that discourse. (cf. various uses of "seed" in Matt. 13)
Comment: I can tell you are well educated in hermeneutics, so to state it more technically, I am trying to caution against the "exegetical fallacy" of "illegitimate totality transfer" (where the connotations of a word in one context are illegitimately carried to another context.)
Comment: Oh, and I am also trying to preserve the distinction between the historical context and the narrative context / between the quoted speaker and the narrator.
Comment: I understand your caution with regards to ITT.  I agree it would be fallacious for instance to arbitrarily equate Paul's use of "seed" in the context of Galatians 3 with "seed" in Matthew 13. They appear in different contexts, have different genres, authors and clearly mean different things. Just like your "lion" example.  BUT each individual authorial work IS a self-contained contextual unite. It should not be partitioned in the same way. Especially when a symbol is clearly invoked without immediate interpretation.  "Night" at Judas' departure (John 13:30) is more than a description of time.
Comment: RE: "each individual authorial work . . . should not be partitioned" I'm not so sure about that. As I mentioned, in Matthew 13 we see "seed" within the same Gospel, *in the same chapter*... in fact, within the same discourse, by the same speaker... being used several different ways.
Comment: When we're talking about very common words like "water," "light," "seed," etc. I think we would do well to remember that these do actually refer to "water," "light," "seed," ... they are not always symbols just because they appear in the same book as a symbolic usage (as your quote from Craig Koester also indicates.) Anyway, you are free to disagree. I am not on a mission to criticize or convince you or anything like that. I hope my comments have been useful to you in some way, but if not, maybe they'll be of some use to another reader.
Comment: Absolutely. Thank you. I do appreciate the discussion.  It truly helps.  My question is what would it take to change your mind?  Is this an ideological objection or is it a point I have yet to prove?  If the later how can I improve the argument?   RE: Matthew 13 "Seed" isn't used altogether differently.  It's the word which germinates as people. And I don't deny that water ceases to be water or light ceases to be light when used symbolically. Thanks again. I'd love to chat more if you're willing.
Comment: let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/8873/discussion-between-jas-3-1-and-matthew-miller)


Four legs vs two legs

Question: How would a four-legged bird's flight differ from a regular two-legged one?
Would it be slower in flight but have more power taking off?
The bird in question is modeled on a bird of prey.
(four legs of equal size and two wings)
Comment: Are we talking four legs and two wings, or some form of quadrupedal bird like bat or pterosaur?
Comment: four legs two wings
Comment: You should really add that to the question it is important.
Comment: Depends on the size of the two extra legs - e.g. they could have T-Rex-like small front legs which they can tuck into their feather during flight - though I suppose they are more arms than legs...
Answer: Any flying bird is aerodynamic. We designed planes from looking at birds, so it makes sense to consider the following:

Weight
Aerodynamics
Purpose

Weight
Adding an extra two legs to a bird is going to add weight. Which could impact is flight capabilities depending on leg thickness and size of bird. A griffon would have more chunky legs versus a pigeon, meaning more weight is being added.
A bird of prey should not have any real trouble with weight since their legs are very small anyway.
Aerodynamics
Here we can see a very elegant eagle, and a bird of prey.

Let's say we add two more legs, where do the legs go? If they go at the front you can clearly see that the bird would lose aerodynamic efficiency, adding them side by side with its current legs most likely wouldn't effect it at all, however I don't see this providing any benefit whatsoever should this be the case. This leads on to purpose.
Purpose
Eagles, owls and all predatory birds hunt using their legs or feet. Adding two more legs could help improve efficiency when hunting but at the same time it could hinder the bird.
For example, an eagle will use two feet, it only has one chance to grab its prey, add another two legs, it now has twice the chance to grab. For the better it becomes easier, but the bird would become lazier and wouldn't rely on precision as much as its two legged friend.
Whether this is a benefit for your scenario then great, but as a general answer to your question, I don't believe it will affect the bird much, although it would not really serve a real purpose.
Unless the bird in question was a mythical creature like a griffon or a hippogriff where its size requires having more than two legs.
Answer: Most vertibrate life on earth follows a 4 limb body plan (in this instance, the wings are two limbs and the legs are the other two).
There are a number of mythical creatures with 6 limbs; Pegasus, griffons, dragons, etc.
One way to get 4 legs and wings is to have the wings double as legs.
Something like the Quetzalcoatlus, which probably used it's wings as extra feet for instance.

But you probably wouldn't want to ride these for long distances on the ground.
Really the only reason to have a flying mount is to fly. A ground animal can carry more weight. It can haul a load. It can wear heavy armor.
If a creature can fly, having limited ground mobility isn't a bad trade. If you need to get somewhere quickly, take off. If you need to get somewhere and don't want to be seen in the air, take a horse.
Answer: I like the idea of a six limbed body plan. If your thing has four legs and two wings it can be more of a hawk, where it uses it's wings to travel but hunts by pouncing from the air and then is basically a lion on the ground. Long jumps for chasing sure. Even powerful enough to carry plenty of weight by the air back to the nest after its made its kill - sure. But don't expect it to be agile or graceful, this is a land predator that can fly.
Contrary-wise you can also have the falcon version of this animal that hunts other flying things (this is an and, not an either or) that has four wings and two stubby talons for ripping up whatever it can catch. This thing would be very fast and maneuverable in the air.
You are looking at creating a whole new taxonomy of griffin like creatures. There's a lot of room here to design what you like.
Comment: Six limbs gives you the potential for four winged birds as well.
Answer: It would depend on the legs, or not.
If an otherwise normally flighted bird has a tiny pair of Tyranosaurus arms, it isn't going to make much difference one way or the other.
If they have a full on second set of drumsticks, they are going to be heavier and not fly as well as if they weren't carrying the extra weight.
Finally... look at existing birds with two legs... some of them take off gracefully and strongly with their legs kicking off under them... others don't use their legs at all... others have to get a running start... still others bounce like beach balls when they attempt to land.
Nature being what it is... 2 more legs can be anything you want it to be if your narrative is thoughtful enough.
Answer: The only flying creatures with more than 2 legs are insects like bees or wasps.
Considering that the take off is an minuscule fraction of the time dedicated to flight, I don't see a clear advantage in having an additional pair of legs.
There might be a small advantage in having more grip on impervious area, but that would be probably overcome by the additional volume needed.
It may be different if the birds are non flying, like emus or ostriches. But in that case it would be better to evolve the unused wings to something like arms, for searching food in the ground or all those funny stuff primates do.
Comment: I thought about giving them an extra pair of legs to make them more maneuverable and practical on the ground as well as in the air. The creatures are going to be used in battle and as a transport method so this seemed like a good idea.
Answer: To answer the first part, only really at take-off and landing since coordinating six limbs is going to be a more complex task than four. Take-off and even more-so landing is going to be restricted to spaces where this bird can get all four feet on a fairly even keel, no landing on thin branches for this critter.
As to flight speed that's about what the bird is designed to do, to be competitive as a bird of prey it needs to be as fast as a modern bird with the same specialty, whether it's a vulture with huge flat gliding wings or a falcon that relies on speed and precision it will have those same characteristics. Whatever it does it is almost certainly going to need a proportionally larger wingspan at a given mass than a two legged bird though because four legs are going to produce more aerodynamic drag.
Answer: In my opinion, such a bird wouldn't be particularly maneuverable due to its center of mass being farther forward than ordinary avians. The difference in take off is negligible as well, sense it would just end up using its back legs to kick off the ground.
However, with two pairs of talons, this birdie could be amazing at climbing and landing on vertical surfaces. Not only that, but they would be able to grab and eat prey without risking a fall. Or maybe they could ambush landing birds, kicking off their perches while ensnaring their prey at the same time. If there spines are flexible enough, they could hunt nimble creatures that use trees as cover, like squirrels or monkeys.
However, regardless of their size, I don't think these hypothetical birds would make good mounts. In order to fly, they would have to have light-weight bones, which can't really support the weight of a human. Of course, a well done aerial combat scene or description of a flying caravan would make me too enraptured with awe to care about bird bones.

Four legs vs two legs


Nexus Mod Manager and Archive Files

Question: The Nexus Mod Manager has my non-steam mod archives stored in C:\Games\Skyrim\mods. Do the archives I have downloaded contain redundant information, and do I need to keep these downloaded copies? Will the archives sorted by NMM be sufficient for the future?
Comment: I think you need to describe the situation better. It seems there are two separate sets of archives, one in NMM mod folder, and another downloaded somehow that is somewhere else? And you think they contain redundant information?
Comment: @Deltharis Yes, that explains it in a much nicer way! I'll change my original post to reflect this, thank you!
Answer: As an answer to this question:
No, you do not need to keep the mod archive files that you have downloaded. NMM seems to make a copy of these archives in the directory you setup for each game. The archives you download from the Nexus or other sites can safely be deleted.

Nexus Mod Manager and Archive Files


Should you always counter the first offer letter?

Question: I just received the first offer letter and it is better than what I asked for. So I am tempted to just accept it but many people and sites say you should always counter. Is it always better to counter asking for more?
Comment: I say if your happy with it take it.  But then I tend to look for value in other things in the workplace over the money package
Answer: There aren't any hard and fast rules about "you MUST counter the first offer" - If you have an offer you like, accept it.
That said, these are the guidelines I've always used:

If you asked for a number and they came back with a higher one - DON'T counter.
They already value you higher than you valued yourself - you will appear to be greedy if you ask for even more.  If you really wanted more money you should have asked for more (when negotiating start with an unreasonable demand and work your way toward what you think they'll accept).
If you asked for a number and they came back with that number - Don't counter.
Or more accurately, be prepared to blow the deal if you do.  You named a number. They agreed. Trying to get more now will be seen as reneging on the deal (because it is: You're renegotiating  after they already agreed to your demands).
Again, if you really wanted more money you should have named a bigger number.
If you asked for a number and they came back below it - Counter if you must.
If the number you named was high and you have a cushion you can consider taking an offer below the number you named (as long as it meets your financial needs).
Of course if you asked for $75,000 and they came back with $50,000 it may be a different story -- I don't usually build in a 33% cushion into my figures :-)
If you didn't ask for a number but they came back with more than you expected - Maybe counter.
You can probably get a little more out of them, most companies make an offer below the maximum they are willing to spend to bring you on board.  Conversely though if they tell you they can't do any better be prepared to accept (or walk away).
If you didn't ask for a number and their offer is below what you are looking for - Think Carefully.
Sure, you might get more money out of them, but if the number is REALLY low the company might also be struggling to make ends meet, or they may consider workers expendable cogs: When you get sick of the low pay, long hours and horrid working conditions you'll quit and they'll get another underpaid peon to do the job.
Working in such an environment is a soul-sucking experience -- Avoid it if at all possible.

I'm also a big proponent of "Make me an offer based on what you think I'm worth" rather than naming a number.  If I am forced to name a number I name a range, and I aim high, for the reasons I already mentioned above.
Comment: +1 Great answer. Bear in mind that an offer usually consist of more than just a salary figure, it will also include other conditions. Make sure that these are aligned with yours as well.
Comment: +1.  You definitely can't counter if the offer is above your   initial demand.
Comment: Thanks. I like the way voretaq7 answered with a little breakdown. A lot of the other answers are "it depends" but you explained the different scenarios.
Comment: @tehnyit Absolutely - Consider the whole compensation package (Salary, Benefits (medical/dental/vision), perks (401(k), IRA, pension), vacation/paid leave allowances), perks (flex time, telecommute, paid transit), and of course the company itself (environment, co-workers, cool stuff to work on).
Comment: If they met your salary requirements you can still counter with benefits improvements (eg. More vacation time).
Comment: @Dunk Quite true - As I said in another comment here, you should always consider the *whole* compensation package (For example, a company that pays you $5K more than you asked for but offers no healthcare package may not be worth it)
Comment: @tehnyit Yes (I agree), *but* some companies will try to use "perks" to simply justify the fact that they are stingy and didn't want to pay you what you asked (or are worth).  See "soul-sucking experience" above.
Comment: @voretaq7 The verb "renege" is almost entirely unrelated to the verb "renegotiate", although that is a nice little mnemonic.
Answer: You were offered more than you asked for.  At this point going back and countering asking for more still will appear greedy.  That is not to say you can not get more but you have an offer that will make you happy.  Why not take that good will and show them that doing right by you is going to pay off.  If you ask for more they could withdraw the offer all together.  So the question is would you rather have more than you asked for for sure.  Or take the risk that you might get more but might lose a great offer?
For what it is worth I did consulting for nearly 20 years.  I only rarely ever countered.  I had an expectation.  If they offer came in below that I either accepted or rejected.  Sometimes they came back with more usually I would reject them anyway.  I have never had an offer come in for more than I asked for.  And I have some fairly good references.
Answer: Don't be greedy. If it's more than you wanted anyway, just take it. You could risk it, but you may end up blowing the opportunity if they decide to revoke their offer altogether and offer it to someone else.
The choice is yours. Choose wisely.
Answer: It's a risk and I would say that what to do depends on:

Your cash.  When is rent due.
The company size.  At a small company it's more likely closer colleagues will know about it.
How good the non-cash intangibles are.
If you have any other offers.
How confident you are about getting another offer quickly.
The hours and if the pay implies 80 hours work for 40 hours pay?
Answer: It depends on what the fair market range is in your area. Do your research and see if they offered you your worth. You can make it clear that you did your research after the interview, and found that they low-balled you. If they'll pull the offer for this reason, I say "good riddance!" You never wanted to work there, I guarantee you.
A lot of times, people go for a job interview prepared just to scale the technical questions as best as they can, without necessarily devoting as much time into researching the fair market price for the position. So I don't think it's fair to make candidates give an expected number in the first place. I think it's better to just ask what they make now, and why they are looking. If they do very well on the interview, you can still try to increase your bottom-line by offering them the lower end of the fair market range if their current or last salary is below the range, and leave it up to them to do their research and negotiate. If they already fall in the fair market range, offer them something between the high end of the range or what your company can afford, if you need them badly, and their current pay. If, on the other hand, they make way more than the fair market range, maybe they should stick with their current job unless they are open to a pay cut, but I think an employer should offer them somewhere near the highest point of the range. All the above, of course, assumes that they are perfectly/best qualified for the position. If, on the other hand, a candidate is desperately looking, they have matched a number "you gave," I say take it.
Comment: I agree with you except the very last sentence. Please don't call out names without explaining why.
Comment: Hello Guest, welcome to The Workplace. We're not a discussion site and instead are a Q&A site, so answers should stand on their own without vaguely referring to other answers. Additionally, we like answers to be supported by facts, references, and specific expertise as per our [back it up rule](http://meta.workplace.stackexchange.com/questions/255/faq-proposal-back-it-up-and-dont-repeat-others). I edited this post to help make it more standalone. Please see [answer] for more details.


How do I choose the proper font & size for my site?

Question: I once saw a textbook that recommended a certain pica range for each of several various fonts.  Is there any online guide that's available?  What are my options? What should I know as a beginner?
Answer: You need to keep in mind that different operating systems (Windows, Mac, Linux) have different  default fonts that come as part of the OS. This means if you choose a font that is available on Windows but not on a Mac or Linux those users will see a different font. That font will be the closest match the OS can choose. If you want your site to look uniform across platforms you'll need to choose fonts that are common to all three. Alternatively you can declare multiple fonts in your CSS in the order of preference you wish them to be used. Example:
/* Sample CSS rule */
p
{
    font-family: arial, helvetica, sans-serif;
}

In this example all
 tags will use the arial font if it is available. If not the browser is to try to use the helvetica font, otherwise it is to try the default sans-serif font. Always make the last font declared a general system default. See this article for 8 font stacks that are safe to use.
Another option is to use the new @font-face CSS rule which allows you to use not standard fonts. You need to provide the font on your website but if a user's browser supports @font-face it will download it and use it. Support for this isn't uniform across browsers and some older browsers don't recognize it yet. But with a little effort it can be used in modern websites.
Font sizes will depend on the font used. The general rule is not to use small fonts as many users will have too much difficulty reading it (basically small fonts are bad accessibility). Also many users like to adjust the font sizes displayed in the browser to make it easier for them to read. If you specify your font sizes using pixels (px) this makes your site harder to use. The general rule is to use empirical units (em) which is a scalable unit and will grow and shrink as the user adjusts their browser display.
Comment: +1 I agree, defining relative sizes (using em or %) is the best we can do. We can only hope, that the user finds out how to do a page zoom (or at least, a text zoom).
Answer: I'm not really sure about the correct answer - but I've learnt that you can't measure in pica on a web site (even if CSS pretends to allow that). And I'm afraid you can't measure in anything, because if a user has a 22" monitor (resolution 1920x1080), the font size will be significantly smaller compared to a 24" monitor with the same resolution. - You can't determine the monitor size from the web page.
Moreover, it also depends enormously on the font: Verdana will appear a lot larger than e. g. Times New Roman.
Having said that, I'd like to see a good guideline, too!


Expression engine 2.1 to 2.11.1 Upgrade never completes

Question: I am trying to do an upgrade from 2.1 to 2.11.1.  I have followed the instructions here https://docs.expressionengine.com/v2/installation/update.html.  My issue when i go through the wizard I get to the portion where it is supposed to start the update and it never finishes or errors out.  It just refreshes every 2 seconds but never gets past that.  I let it sit for a couple of hours and never got past that screen.
I then went in to try and get the login page but I get this error.

Error
Unable to load requested field type file:  ft.rel.php.
Confirm the fieldtype file is located in the
  expressionengine/third_party/ directory

I noticed a change with the filetype folder where each file type is now in its own folder and also rel went to relationship.  I made sure I copied /system/expressionengine/fieldtypes/relationship/ft.relationship.php and saved it to /system/expressionengine/fieldtypes/ft.rel.php and /system/expressionengine/third_party/ft.rel.php.  This did not make the error go away.
Any advice on what to try next would be appreciated.
Thanks
UPDATE
I have gotten past this point now.  I went in and manually changed a couple of things in the database.  First I changed rel to relationship in exp_fieldtypes table.  Second I changed all references to rel to relationship in exp_channel_fields.
I am now able to see the login page but I am not able to login.  I get the following error.

The following errors were encountered
This form has expired. Please refresh and try again.

I have read some places it could be because of cookies or cache but fixing those did not help at all.  I found the error occurs because of an expired csrf token.  In my case no csrf token.
So again I am stuck as the issue is the upgrade wizard does not do what it is supposed to do.
Wondering if anyone else has had a similar issue with the upgrade wizard from any version of 2 past 2.6 which is where I believe csrf tokens were implemented.  Any tips would be appreciated.
Answer: Looks like the issue was because the config file was setup to grab a different config file for each environment.  Even though I set it up the same way it causes the upgrade wizard to stall.  Once I copied my dev config file to the base config file the upgrade proceeded as planned.  Then I switched back the base config file to use env specific conf files it worked.


How can I make the sound of fly or mosquito?

Question: I wonder how can I make the sound of a mosquito or a fly or any kind of insect? I prefer a comic sound.
Answer: A bread and butter way is using a comb with thin paper, put the paper on top of the comb, covering the upside completely, with the teeth pointing at you, and blow between them. Might take a little practice, but does indeed work well!
Answer: Jimmy Macdonald was Disney's first sound effects designer and he is responsible for so many of the quintessential cartoon sounds that we associate with. He does a pretty good job of the talking fly/mosquito sound using rubber tubing attached to a kind of drum skin. You can see a demonstration of the sound in this documentary (highly recommended viewing for some general inspiration).
Disney Family Album #4 - Jimmy MacDonald
Answer: Rub your knuckles or finger nails fast enough. Record about 20-30 seconds, use a high-pass filter on the recording to get rid of the unnecessary low end, then pitch it up until you get a buzzing sound. It would resemble little wings. :)
You can use various objects to get different timbres with this technique.
Answer: I made a video to answer your question:
Use FL Studio, and use a violin plugin like here

get a single violine synth

use panning filter on it

filter it with equalizer

automate the volume
Answer: Press your lips together real tight and then force the air in your mouth out between your lips so they vibrate at a very high pitch.
You can very (vairy?) the pitch by loosening or tightening your lips or using your mouth muscles to change the shape of your lips.
I find this very comical when a dog or a cat is in the room.


How can I retrieve the WEP password

Question: How can I retrieve the WEP password for the 2wire774 wireless router so I can operate another computer on the network?
Answer: If its on windows computer you have already connects to the router nirsoft wireless key view should be able to recover a hashed version. He also has a router password recovery tool that, while not supporting your model explicitly, is worth a try.
Answer: Was this router supplied by your ISP?  Some ISPs will print the WEP code on a sticker on the router.  If its not there, call your ISP, they either know it, or know how to reset your router to default settings to get the default password.
If this router was purchased by you, and you didnt change the password, you should be able to read the manual to get the default password.  Also, the manual will tell how to reset the router to default settings so you can use the default password.
If you ever reset your router to get the default password, you should change the password!
Answer: If all else fails:
Googling for a possible answer I came across a mysterious file containing a hash associated with the 2wire774:
3e0cb3c29e6263a9d4ed46d272fe4433
I have no idea what the hash actually is for, but it could the MD5 for the master password.
You would then have to use one of the many MD5 cracking sites in an attempt to recover the password.
BTW, did you try some strings that might be the default password?
Answer: Open a web browser and log into the setup page on your router. WEP uses
"encryption keys", not passwords, and it will be shown in the basic wireless
settings.

How can I retrieve the WEP password


How do I prove equality of x and y?

Question: If $0\leq x,y\leq\frac{\pi}{2}$ and $\cos x +\cos y -\cos(x+y)=\frac{3}{2}$, then how can I prove that $x=y=\frac{\pi}{3}$?
Your help is appreciated.I tried various formulas but nothing is working.
Comment: 38 minutes. $ $
Answer: Here's a sketch: Consider $y\in[0,\pi/2]$ as fixed, and let $f(x)=\cos x + \cos y - \cos(x+y)$. Locate the maximum of $f$ on $[0,\pi/2]$ by solving $f'(x)=0$ for $x$; you'll find that the largest value is
$$
f\left(\frac{\pi}{2}-\frac{y}{2}\right)=\frac{3}{2}-2 \left(\sin\frac{y}{2}- \frac{1}{2}\right)^2.
$$
Maybe you can finish it from there?
Comment: Thank you, but I am not allowed to use calculus.
Comment: Unfortunately, I cannot accept both answers.:)
Answer: $cos x +cos y -cos(x+y)=2\cos(\frac{x+y}{2})\cos(\frac{x-y}{2})-(2\cos^2(\frac{x+y}{2})-1)=2\cos(\frac{x+y}{2})\cdot\left(\cos(\frac{x-y}{2})-cos(\frac{x+y}{2})\right)+1\le $
$2\cos(\frac{x+y}{2})\cdot\left(1-cos(\frac{x+y}{2})\right)+1\le 1/2+1=\frac{3}{2}$, where the inequality is by $ab\le (\frac{a+b}{2})^2$, so $\cos(\frac{x+y}{2})\cdot\left(1-cos(\frac{x+y}{2})\right)\le 1/4$ . The equality holds iff $x=y=\pi/3$.
Answer: Algebraic but cumbersome: express the condition in terms of $a=\mathrm e^{\mathrm ix}$ and $b=\mathrm e^{\mathrm iy}$ and solve.
One knows that $2\cos(x)=a+a^{-1}$, $2\cos(y)=b+b^{-1}$, and $2\cos(x+y)=ab+a^{-1}b^{-1}$ since $ab=\mathrm e^{\mathrm i(x+y)}$. Multiplying everything by $ab$ to get rid of the denominators, one gets
$$
a(1-a)b^2+(a^2+1-3a)b+a-1=0.
$$
Solving the second degree equation with unknown $b$ yields
$$
b^{-1}=1-a\quad\mbox{or}\quad b=1-a^{-1}.
$$
Either $b^{-1}=1-a$, then $|1-a|=1$ hence $a$ is on both circles of radius $1$ centered at $0$ and at $1$, that is $x=\pm\pi/3$, and $y=x$ since $1-a=a^{-1}$.
Or $b=1-a^{-1}$, then $a^{-1}=1-b$ hence the solution is the same than in the first case, exchanging the roles of $x$ and $y$.
Finally, the condition that $x$ and $y$ are in $[0,\pi/2]$ imposes that $x=y=+\pi/3$.
Answer: You could also attempt an geometric proof. First, without loss of generality you can assume
$0 <x,y < \frac{\pi}{2}$.
Construct a triangle with angles $x,y, \pi-x-y$.
Let $a,b,c$ be the edges. Then by cos law, you know that
$$\frac{a^2+b^2-c^2}{2ab}+ \frac{a^2+c^2-b^2}{2ac}+ \frac{b^2+c^2-a^2}{2bc}=\frac{3}{2}$$
and you need to show that $a=b=c$.
The inequality is
$$c(a^2+b^2-c^2)+b(a^2+c^2-b^2)+a(b^2+c^2-a^2)=3abc$$
or
$$a^2b+ab^2+ac^2+a^2c+bc^2+b^2c=a^3+b^3+c^3+3abc \,.$$
This should be easy to factor, but I fail to see it....

How do I prove equality of x and y?