SOLUTION: Prove the following identity: cos 4x = cos^4x - 6cos^2xsin^2s + sin^4x

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Question 32481: Prove the following identity:
cos 4x = cos^4x - 6cos^2xsin^2s + sin^4x
Answer by venugopalramana(3286) About Me  (Show Source):
You can put this solution on YOUR website!
COS(4X)=COS(2(2X))=COS^2(2X)-SIN^2(2X)
={COS^2(X)-SIN^2(X)}^2-{2SIN(X)COS(X)}^2
=COS^4(X)+SIN^4(X)-2COS^2(X)SIN^2(X)-4SIN^2(X)COS^2(X)
=COS^4(X)-6COS^2(X)SIN^2(X)+SIN^4(X)