Question

Use basic identities to simplify the expression.

cos θ - cos θ sin2θ

Answer 1

\[\sin(2\theta)=2\sin(\theta)\cos(\theta)\]
\[\cos( θ) - cos( θ) sin(2θ)=cos( θ)(1-sin(2θ))\]
\[\cos( θ)(1-2\sin(\theta)\cos(\theta))\]
\[=cos( θ)-2\sin(\theta)\cos^2(\theta)\]