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# Edexcel C2 20th May 2015 *Official Thread* watch

1. (Original post by userxx990)
Yess sorry thats squared! how did you get 1/2 t? ive looked at the logs rule but still cant figure it out..

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2. (Original post by LearningGeek)
Log of X to the base a = Log of X to the base b / log of a to the base b

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Hmm ok so then how can log x to the base 9 equal to 2?
3. (Original post by Supermanxxxxxx)
I'll do that for you step by step give me like 5 mins

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Ok waiting

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4. (Original post by userxx990)
Hmm ok so then how can log x to the base 9 equal to 2?
It doesnt

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5. (Original post by lulupixie)
Thank you! I'll drop you a message if I need any help! Good luck for Tuesday, you'll be fine! x
Yes- anytime! Haha, now that's what I'm awfully worried about loll. Thanks also,

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6. (Original post by studentwiz)
how did you know 1/6 is shaded in?
and
how did you know thetha = pi-2/3pi
1/6 is implied by the answer and Pi - 2/3 pi is because we are using radians to find the angle and seeming as all of the angles are equal to each other when divided by 3 i knew i had to use this.
7. (Original post by TrentL)
1/6 is implied by the answer and Pi - 2/3 pi is because we are using radians to find the angle and seeming as all of the angles are equal to each other when divided by 3 i knew i had to use this.
why did you then tan thetha?
8. (Original post by studentwiz)
why did you then tan thetha?
to convert this into a radians degree
9. Thanks! :'D
10. I got 6 different solutions for x that all lie within the range.
11. Have you got the mark scheme to this because I'd like to see if the following is right or wrong
X = 15, 25, 75, 85, 135, 145
12. (Original post by ChemFemme)
Have you got the mark scheme to this because I'd like to see if the following is right or wrong
X = 15, 25, 75, 85, 135, 145
https://qualifications.pearson.com/c...c_20120123.pdf
q9
13. (Original post by ChemFemme)
Have you got the mark scheme to this because I'd like to see if the following is right or wrong
X = 15, 25, 75, 85, 135, 145
Hey! I got the same answers as the person above: 15, 55, 135, 175

Have you got your working out? If you show me it, I could try and point out where you may have gone wrong?
14. (Original post by Anon_98)
Yes- anytime! Haha, now that's what I'm awfully worried about loll. Thanks also,

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Just worked out I think I can do binomials and factor theorem stuff, that rules two things out 😂 good luck you will be fine! Trust me I think my friend has the same
15. Which past paper do people reckon is the hardest that they've done, just the standard ones not Solomon.
16. (Original post by mrchemistry)
Hey! I got the same answers as the person above: 15, 55, 135, 175

Have you got your working out? If you show me it, I could try and point out where you may have gone wrong?
Let theta be 3x-15
Sintheta = 1/2
I drew the graph up until 450
Drew horizontal line from 1/2
Theta = 30, 60, 210, 240, 390, 420
3x-15 = The above
x = 15, 25, 75, 85, 135, 145 and anymore values would lie out of range 0<x<180
17. (Original post by Elinh)
Does anyone here know a good place to revise logs? i'm good with most of C2 but I loose so many marks from messing up log questions.

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go onto exam solutions, watch his videos on how to solve log questions, do the exam questions under that heading.
18. (Original post by ChemFemme)
Let theta be 3x-15
Sintheta = 1/2
I drew the graph up until 450
Drew horizontal line from 1/2
Theta = 30, 60, 210, 240, 390, 420
3x-15 = The above
x = 15, 25, 75, 85, 135, 145 and anymore values would lie out of range 0<x<180
I think I can see where you've gone wrong. Basically what you should do is:

sin(3n-15) = 0.5
therefore 3n-15 = sin^-1(0.5)
therefore 3n-15 = 30 (this is your first value)
Draw CAST diagram...and since the sin value is positive, the value will be in first and second quadrant (top right and top left). So the angle will be 30, and 180-30 which is 150.

So 3n-15 = 30, 150...you then add 360 to both of these to get 390, 510, and then add 360 to those 2 to get 750, 870 (do this just incase the final values are in range)

so 3n-15 = 30,150,390,510,750, 870
therefore 3n = 45,465,405,525,675,885
therefore n = 15,55,135,175 (to fit that range of 0 to 180)

I hope that made sense! It's hard to type it all out, on paper it's a lot shorter
19. (Original post by mrchemistry)
I think I can see where you've gone wrong. Basically what you should do is:

sin(3n-15) = 0.5
therefore 3n-15 = sin^-1(0.5)
therefore 3n-15 = 30 (this is your first value)
Draw CAST diagram...and since the sin value is positive, the value will be in first and second quadrant (top right and top left). So the angle will be 30, and 180-30 which is 150.

So 3n-15 = 30, 150...you then add 360 to both of these to get 390, 510, and then add 360 to those 2 to get 750, 870 (do this just incase the final values are in range)

so 3n-15 = 30,150,390,510,750, 870
therefore 3n = 45,465,405,525,675,885
therefore n = 15,55,135,175 (to fit that range of 0 to 180)

I hope that made sense! It's hard to type it all out, on paper it's a lot shorter
I've stopped using cast diagrams for various reasons. Thanks, that did help .

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