Question

Verify each identity:
cos^2x-sin^2x=2cos^2x-1

Answer 1

\(\bf {\color{blue}{ sin^2(\theta)+cos^2(\theta)=1\implies sin^2(\theta)=1-cos^2(\theta)}}\\ \quad \\ \quad \\
cos^2(x)-sin^2(x)\implies cos^2(x)-[{\color{blue}{ 1-cos^2(\theta)}}]\)

expand that, see what you get

Answer 2

Thank you!! :)