\[1)\ \left\lbrack \frac{\pi}{2};\ \frac{3\pi}{2} \right\rbrack:\]
\[\left\lbrack \pi;\ \frac{3\pi}{2} \right\rbrack\ и\ \left\lbrack \frac{\pi}{2};\ \pi \right\rbrack.\]
\[2)\ \left\lbrack - \frac{\pi}{2};\ \frac{\pi}{2} \right\rbrack:\]
\[\left\lbrack - \frac{\pi}{2};\ 0 \right\rbrack\ и\ \left\lbrack 0;\ \frac{\pi}{2} \right\rbrack.\]
\[3)\ \left\lbrack 0;\ \frac{3\pi}{2} \right\rbrack:\]
\[\left\lbrack \pi;\ \frac{3\pi}{2} \right\rbrack\ и\ \lbrack 0;\ \pi\rbrack.\]
\[4)\ \left\lbrack - \pi;\ \frac{\pi}{2} \right\rbrack:\]
\[Ответ:\ \ \lbrack - \pi;\ 0\rbrack\ и\ \left\lbrack 0;\ \frac{\pi}{2} \right\rbrack.\]