Interesting proof...

Question

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

Pangolin14 Dec 14, 2020

Melody · Answer 1 · 2020-12-14T11:25:28

This is a super easy proof.

Hint: $Cos(2A)=cos^2A-sin^2A$

Pangolin14 · Answer 2 · 2020-12-14T07:01:19

Ah, yes. Law of cosines.