cos2x formula? What is cos2x formula

Cos 2x Formula

\cos(2x) = \cos(x + x)

= \cos(x)\cos(x)-\sin(x)\sin(x)

= \cos^2(x) - \sin^2(x)

cos2x = cos^2x - sin^2x

cos2x = 2cos^2x - 1

cos2x = 1 - 2sin^2x

cos2x = (1 - tan^2x)/(1 + tan^2x)