Question

Solve the inequalities:
$\cos x\le -\frac{1}{2}$

Answer 1

$\cos x\le -1/2\cos x\le \cos 120°x\le 120°(\cos$

is a decreasing function)

$x\le \frac{2\pi }{3},xϵ(\frac{2\pi }{3},\pi )$