The value of the expression $2 \sec^{-1} 2 + \sin^{-1} \left( \frac{1}{2} \right)$ is |
$\frac{\pi}{6}$ $\frac{5\pi}{6}$ $\frac{7\pi}{6}$ $1$ |
$\frac{5\pi}{6}$ |
The correct answer is Option (2) → $\frac{5\pi}{6}$ ## We have, $2 \sec^{-1} 2 + \sin^{-1} \frac{1}{2} = 2 \sec^{-1} \left( \sec \frac{\pi}{3} \right) + \sin^{-1} \left( \sin \frac{\pi}{6} \right)$ $\left[ ∵\sec \frac{\pi}{3} = 2 \text{ and } \sin \frac{\pi}{6} = \frac{1}{2} \right]$ $= 2 \cdot \frac{\pi}{3} + \frac{\pi}{6} \quad [∵\sec^{-1}(\sec x) = x \text{ and } \sin^{-1}(\sin x) = x]$ $= \frac{4\pi + \pi}{6} = \frac{5\pi}{6}$ |