Question

Plzzz Derive the formula of cos3x.​

Answer 1

ANSWER♥️

ANSWER REFER TO THE ATTACHMENT

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Answer 2

SOLUTION

cos(3x)

$= > cos(3x) = cos(2x + x) \\ = > cos(2x)cosx - sin(2x)sinx \\ = > ( {cos}^{2} x - sin {}^{2} x)cosx - 2sin {}^{2} x cosx \\ = > {cos}^{3} x - (1 - cos {}^{2} x)cosx - 2(1 - {cos}^{2} x)cosx \\ = > 2cos {}^{3} x - cosx + cos {}^{3} x - 2cosx \\ = > 4cos {}^{3} x - 3cosx$

hope it helps ☺️