Answer
$\theta=2k\pi+\frac{5\pi}{6}$ or $2k\pi+\frac{7\pi}{6}$ (k is an integer),
$\theta=\frac{5\pi}{6}, \frac{7\pi}{6},\frac{11\pi}{6},\frac{13\pi}{6},\frac{17\pi}{6},\frac{19\pi}{6}$.
Work Step by Step
$cos\theta=-\frac{\sqrt 3}{2}$,
$\theta=2k\pi+\frac{5\pi}{6}$ or $2k\pi+\frac{7\pi}{6}$ (k is an integer),
Six examples: $\theta=\frac{5\pi}{6}, \frac{7\pi}{6},\frac{11\pi}{6},\frac{13\pi}{6},\frac{17\pi}{6},\frac{19\pi}{6}$.
