Question

Cos2x+cos10x=0 Пожалуйста помогите

Answer 1

$\cos2x+\cos10x=0\\\\ 2\cos(\frac{2x + 10x}{2})\cos(\frac{10x - 2x}{2}) = 0\\\\ \cos6x\cos4x = 0\\\\ 1. \cos4x = 0\\\\ \boxed{x = \frac{\pi}{8} + \frac{\pi n}{4} , \ z \in \mathbb{Z}}\\\\ 2. \cos6x = 0\\\\ \boxed{x = \frac{\pi}{12} + \frac{\pi n}{6} , \ z \in \mathbb{Z}}$