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

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Question 953244: Find the exact value by using a half-angle identity.
cosine of five pi divided by twelve.
Answer by Alan3354(69443) 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.
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cos(5pi/12)
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cos(5pi/6) = -sqrt(3)/2
Use cos^2(x/2), it's simpler than cos(x/2)
cos^2(x/2) = (1 + cos(x))/2
cos%5E2%285p%2F12%29+=+%281+-+sqrt%283%29%29%2F2+=+%282+-+2sqrt%283%29%29%2F4
cos%285pi%2F12%29+=+sqrt%282+-+2sqrt%283%29%29%2F2 (positive in Q2)