Question

Вычислить тригонометрические неравенства:

Answer 1

$\displaystyle \cos \frac{x}{3}<\frac{\sqrt{2}}{2}\\ \\ \\ \frac{\pi}{4}+2\pi n < \frac{x}{3}<\frac{7\pi}{4}+2\pi n,n \in \mathbb{Z}\\ \\ \\ \boxed{\frac{3\pi}{4}+6\pi n<x<\frac{21\pi}{4}+6\pi n,n \in \mathbb{Z}}$