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Given that x and n are real numbers, prove that $cos(nx) = cos^2(\frac{n}{2} x) - sin^2(\frac{n}{2} x).$

 Dec 14, 2020
 #1
avatar+112827 
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This is a super easy proof.

 

Hint:    \(Cos(2A)=cos^2A-sin^2A\)

 Dec 14, 2020
 #2
avatar+419 
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Ah, yes. Law of cosines.

 Dec 14, 2020

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