Express-cos-4x-interm-of-cos-x-

Question Number 115248 by aye48 last updated on 24/Sep/20

Express \cos 4 x interm of \cos x .

Answered by Olaf last updated on 24/Sep/20

\cos 4 x = {2 \cos}^{2} 2 x - 1

\cos 4 x = 2 {({2 \cos}^{2} x - 1)}^{2} - 1

\cos 4 x = 2 ({4 \cos}^{4} x - {4 \cos}^{2} x + 1) - 1

\cos 4 x = {8 \cos}^{4} x - {8 \cos}^{2} x + 1

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