Evaluate the following expressions. Your answer must be an angle $-\pi/2 \le \theta \le \pi$ in radians.
$\sin^{-1}(-\frac{\sqrt{3}}{2})$
$\sin^{-1}(\frac{1}{2})$
$\cos^{-1}(-\frac{\sqrt{3}}{2})$
$\cos^{-1}(\frac{\sqrt{3}}{2})$