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Old October 31st, 2009, 04:54 PM
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Default I need some hints on proving an identity

sin^4x + 2sin^2x cos^2x + cos^4x = 1

Alright. I wouldn't like to know the solution, but I would like some help in solving this.

It looks to me like I need to do a lot of simplifying. A thing I do know:

sin^2x+cos^2x=1

I'm not sure, but I think if you rearranged the terms you could get sin^4x+cos^4x+2sin^2xcos^2x and then maybe break up the sin^4x+cos^4x into (sin^2x)(sin^2x)+(cos^2x)(cos^2x). Maybe do that for the other term as well? (sinx)(sinx)(cosx)(cosx).
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