# Easy Easy Trig help

• November 27th 2009, 08:11 PM
jgv115
Easy Easy Trig help
A cone is 15cm high and has a semi-vertical angle of 18 degrees.

I'm quite good at trigonometry but I just don't get this question can someone help me?

• November 27th 2009, 09:06 PM
bigwave
the semi vertical angle of a cone is the angle
between the axis and a line in the surface which passes through the apex.
• November 27th 2009, 10:14 PM
jgv115
Ok I think I get it. So I have to find the radius

so if I make a right angled triangle...

$\sin 18 = \frac {x}{15}$

$x = 15*\sin 18$

$= 4.64$

is this right?
• November 27th 2009, 11:09 PM
bigwave
Quote:

Originally Posted by jgv115
Ok I think I get it. So I have to find the radius

so if I make a right angled triangle...

$\sin 18 = \frac {x}{15}$

$x = 15*\sin 18$

$= 4.64$

is this right?

seems so...
don't forget units especially on a test
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