SOLUTION: Find the exact value by using a half-angle identity. cos(-pi/8)

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Question 769452: Find the exact value by using a half-angle identity.
cos(-pi/8)
Answer by tommyt3rd(5050) About Me  (Show Source):
You can put this solution on YOUR website!
cosine is an even function so
cos%28-pi%2F8%29=cos%28pi%2F8%29

cos%28%28pi%2F4%29%2F2%29=sqrt%28%281%2Bcos%28pi%2F4%29%29%2F2%29