$\frac{\pi}{2}$

$\frac{\pi}{3}$

$\frac{\pi}{6}$

$\frac{\pi}{4}$

$(4 n+1) \frac{\pi}{2}, n \in Z$

$2 n \pi+\frac{\pi}{3}, n \in Z$

$n \pi+\frac{\pi}{2}, n \in \mathbf{Z}$

$2 n \pi+\frac{\pi}{6}, n \in \mathbf{Z}$

$2 n \pi \pm \frac{\pi}{4}+\frac{\pi}{12}$

$n \pi+(-1)^n \frac{\pi}{4}+\frac{\pi}{12}$

$2 n \pi \pm \frac{\pi}{4}-\frac{\pi}{12}$

$n \pi+(-1)^n \frac{\pi}{4}-\frac{\pi}{12}$

$\left\{\frac{\theta}{\theta}=2 n \pi \pm \frac{\pi}{3}, n \in \mathbf{Z}\right\}$

$\left\{\frac{\theta}{\theta}=n \pi+(-1)^n \frac{\pi}{2}, n \in \mathbf{Z}\right\}$

$\left\{\frac{\theta}{\theta}=n \pi+\frac{\pi}{6}, n \in \mathbf{Z}\right\}$

$\phi$