Question

prove the identity cos4θ = 1- 8 sin^2θ cos^2θ

Answer 1

first use
\[\cos 4\theta = 1 - 2 \sin^{2}2\theta \]

Answer 2

then use
\[\sin 2 \theta = 2\sin \theta \cos \theta\]
to expand
\[\sin^{2 }2\theta\]

Answer 3

then u will get ur answer :) ...can u do it ?