Question

Verifying trig identity :cos to the second power theta minus sin to the second power theta  equals 1 minus 2 sin to the second power theta

Answer 1

$\vdots\ sin^2\theta+cos^2\theta=1\to cos^2\theta=1-sin^2\theta\ \vdots\\\\\\cos^2\theta-sin^2\theta=1-2sin^2\theta\\\\L=\underbrace{1-sin^2\theta}_{cos^2\theta}-sin^2\theta=1-2sin^2\theta=R\\\\L=R$