\[1)\ \left\lbrack \pi;\ \frac{3\pi}{2} \right\rbrack:\]
\[y = \sin x.\]
\[2)\ \left\lbrack 0;\ \frac{\pi}{2} \right\rbrack:\]
\[y = \cos x.\]
\[3)\ \left\lbrack - \pi;\ - \frac{\pi}{2} \right\rbrack:\]
\[y = \sin x.\]
\[4)\ \left\lbrack \frac{\pi}{2};\ \pi \right\rbrack:\]
\[y = \sin x;\ y = \cos x.\]