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XsaiX
 Post subject: First Powers of Cosine
PostPosted: Sat, 28 Jan 2012 17:58:06 UTC 
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How do you write sin^4(3x) in terms of the first powers of cosines of multiple angles?
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Shadow
 Post subject: Re: First Powers of Cosine
PostPosted: Sat, 28 Jan 2012 18:07:38 UTC 
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XsaiX wrote:
How do you write sin^4(3x) in terms of the first powers of cosines of multiple angles?


\cos(2x)=2\cos^2(x)-1=1-2\sin^2(x) use that to reduce down to quadratic, then reduce once more.

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