SOLUTION: Prove the identity: cos^2 y - sin^2 y = 1-2sin^2 y

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Question 1104466: Prove the identity:
cos^2 y - sin^2 y = 1-2sin^2 y
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
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Prove the identity:
cos^2(y) - sin^2(y) = 1 - 2sin^2(y).
~~~~~~~~~~~~~~~~~ 

  cos^2(y) - sin^2(y) =      (substitute here cos^2(y) = 1 - sin^2(y) to get) 


= 1 - 2*sin^2(y).

QED.