Posted by **Anonymous** on Sunday, April 15, 2012 at 12:01am.

Prove the identity: cos^4(x)-sin^4(x)=1-2sin^2(x).with explanation

im confused on this one cause of the 4th power of the sine. does this mean that we put it in the calculator 4 times? and what exactly does it mean by prove the identity- does it mean like make sure both sides equal each other?

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