Question

Первая cos5x≥-√3/2 вторая ctg 2x> -1

Answer 1

$cos5x \geq - \frac{ \sqrt{3} }{2} \\\ - \frac{5 \pi }{6}+2 \pi n \leq 5x \leq \frac{5 \pi }{6}+2 \pi n$
$- \frac{ \pi }{6}+ \frac{2 \pi n}{5} \leq x \leq \frac{ \pi }{6}+ \frac{2 \pi n}{5}$

$ctg 2x-1 \\\ \pi n<2x < \frac{3 \pi }{4}+ \pi n$
$\frac{\pi n}{2}$$<$$x$$<$$\frac{3\pi}{8}+\frac{\pi n}{2}, n\in Z$