Question

...Тригонометрические уравнения

Answer 1

$\cos x\cos2x-\sin x\sin 2x=0 \\ \cos(x+2x)=0 \\ \cos 3x=0 \\ 3x= \frac{\pi}{2} + \pi n,n \in Z \\ x= \frac{\pi}{6} + \frac{\pi n}{3} , n \in Z$

$\sin^2x=-(\cos^2x-\sin^2x)\\ \sin^2x+\cos x-\sin^2x=0 \\ \cos x=0 \\ x= \frac{\pi}{2} + \pi n,n \in Z$