In $[0,2\pi ],S_1,S_2,S_3$ are the number of solutions for the following trigonometric equations.

1)  $\sin \theta =1$       2)  $\sin \theta =-\frac{1}{2}$     3)  $\sin \theta =2$

$\sin \theta =1$ have one solution in $[0,2\pi ],S_1=1$

$\sin \theta =-\frac{1}{2}=-\sin 30$

$\begin{array}{l}\sin (180°+30°)=-\sin 30°\\ \sin (360°-30°)=-\sin 30°\end{array}\}$has two solutions,  $S_2=2$

$\sin \theta =2$ has no solution,  ${\text{S}}_3=0$

$S_3<S_1<S_2$