Question

Cos^2(720-x)+sin^2(540+x)

Answer 1

$\mathtt{\cos^2(720а-x)+\sin^2(540а+x)=\cos^2(2\pi-x)+\sin^2(\frac{3\pi}{2}+x)=}\\\mathtt{\cos^2x+(-\cosx)^2=\cos^2x+\cos^2x=2cos^2x=cos2x+1}$