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Prove by PMI, cos x. cos 2x. cos 4x. cos (2^{n-1} x) = sin 2^{x} a/ 2^{x} sin a

Refer the following similar link:

https://www.meritnation.com/ask-answer/question/cosx-cos2x-cos4x-cos-2-n-1-x-sin2-n-x-2-n-sinx-prov/principle-of-mathematical-induction/8246063

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