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?

Thanks in advance

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- Nov 27th 2009, 08:11 PMjgv115Easy 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?

Thanks in advance - Nov 27th 2009, 09:06 PMbigwave
the

of a cone is the angle*semi vertical angle*

between the axis and a line in the surface which passes through the apex. - Nov 27th 2009, 10:14 PMjgv115
Ok I think I get it. So I have to find the radius

so if I make a right angled triangle...

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

$\displaystyle x = 15*\sin 18 $

$\displaystyle = 4.64 $

is this right? - Nov 27th 2009, 11:09 PMbigwave