Chapter 13, Trigonometric Ratios and Functions - 13.4 Evaluate Inverse Trigonometric Functions - 13.4 Exercises - Quiz for Lessons 13.3-13.4 - Page 880: 12

$60^{\circ}$ or, $\dfrac{\pi}{3}$

Here, we have $\cos^{-1} (\dfrac{1}{2})$ This means that $\theta=\cos^{-1} (\dfrac{1}{2})$ This gives : $\theta=60^{\circ}$ The range of the function $arccos$ is from $[0, 180^{\circ}]$. Hence, we have $\theta=60^{\circ}$ or, $\dfrac{\pi}{3}$