# What are Double Angle Identities?

Nov 6, 2014

Double Angle Identities

$\sin 2 \theta = 2 \sin \theta \cos \theta$

$\cos 2 \theta = {\cos}^{2} \theta - {\sin}^{2} \theta = 2 {\cos}^{2} \theta - 1 = 1 - 2 {\sin}^{2} \theta$

$\tan 2 \theta = \frac{2 \tan \theta}{1 - {\tan}^{2} \theta}$

I hope that this was helpful.