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August 21, 2014

August 21, 2014

Posted by **Steve** on Wednesday, December 16, 2009 at 10:06pm.

- trig -
**Reiny**, Wednesday, December 16, 2009 at 10:20pmI am going to use

cos 2A = 1 - 2sin^2 A

or

cos è = 1 - 2sin^2 (è/2)

so we first have to know cos è

make a diagram using sin è = 1/4

then cos è = √15/4

back in our equation...

√15/4 = 1 - 2sin^2 (è/2)

which solves to √[(4-√15)/8]

(I tested my answer on a calculator)

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