Question

Решите неравенство:
|cos2x+1|<1 

Answer 1

$|cos2x+1|<1\begin{cases}cos2x+1<1 \cos2x+1>-1 end{cases}Rightarrowbegin{cases}cos2x<0 \cos2x>-2 end{cases}Rightarrowcos2x<0\ fracpi2+2pi n<2x<frac{3pi}2+2pi n\frac{pi}4+pi n<x<frac{3pi}4+pi n,;;ninmathbb{Z}$