SOLUTION: Find the exact value by using a half-angle identity. cosine of five pi divided by twelve.

Algebra ->  Trigonometry-basics -> SOLUTION: Find the exact value by using a half-angle identity. cosine of five pi divided by twelve.      Log On


   

Question 1017962: Find the exact value by using a half-angle identity.
cosine of five pi divided by twelve.
Found 2 solutions by lwsshak3, MathTherapy:
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Find the exact value by using a half-angle identity.
cosine of five pi divided by twelve.
cos x/2=sqrt%281-cos+x%29%2F2
cos 5pi/12=cos(5pi/6/2=sqrt%281-cos+5pi%2F6%29%2F2=sqrt%281-sqrt%283%29%2F2%29%2F2

Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!

Find the exact value by using a half-angle identity.
cosine of five pi divided by twelve.
cos+%281%2F2%29A+=+%22+%22%2B-+sqrt%28%281+%2B+cos+%28A%29%29%2F2%29

cos+%28%285pi%29%2F12%29%29%29, or cos+%281%2F2%29%28%285pi%29%2F6%29 = +sqrt%28%281+%2B+cos+%28%285pi%29%2F6%29%29%2F2%29 = sqrt%28%281+%2B+%28-+sqrt%283%29%2F2%29%29%2F2%29 = sqrt%28%281+-+sqrt%283%29%2F2%29%2F2%29 = sqrt%28%282%2F2+-+sqrt%283%29%2F2%29%2F2%29 = sqrt%28%28%282+-+sqrt%283%29%29%2F2%29%2F2%29%29 = sqrt%28%282+-+sqrt%283%29%29%2F4%29%29 = highlight%28highlight_green%28highlight%28sqrt%282+-+sqrt%283%29%29%2F2%29%29%29