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(52790)
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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.
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