SOLUTION: Prove the formula for Cos5A

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Question 1143136: Prove the formula for Cos5A
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
What formula?
There are many.
Here's one:
cos%285A%29+=+sqrt%281+-+sin%5E2%285A%29%29
Look up "Half angle formulas" on Wikipedia.