# How do you calculate the Cos^-1 (1/2)?

The pricipal value of $\theta = {\cos}^{-} 1 x$ should
$0 \le \theta \le \pi$
So ${\cos}^{-} 1 \left(\frac{1}{2}\right) = {\cos}^{-} 1 \left(\cos \left(\frac{\pi}{3}\right)\right) = \frac{\pi}{3}$