Target Exam

CUET

Subject

Maths. Section B1

Chapter

Inverse Trigonometric Functions

Question:

The value of $sin[\frac{π}{2}-sin^{-1}(-\frac{\sqrt{3}}{2})]$ is:

Options:

$\frac{1}{2}$

$\frac{1}{\sqrt{2}}$

$\frac{\sqrt{3}}{2}$

$-\frac{\sqrt{3}}{2}$

Correct Answer:

$\frac{1}{2}$

Explanation:

The correct answer is option 1: $\frac{1}{2}$

The principal value of $\sin^{-1}\left( -\frac{\sqrt{3}}{2} \right)$ is $-\frac{\pi}{3}$.

The principal value range of $\sin^{-1} x$ lies between $-\frac{\pi}{2}$ and $\frac{\pi}{2}$.

Substituting $-\frac{\pi}{3}$ :

$\sin\left[ \frac{\pi}{2} - \left( -\frac{\pi}{3} \right) \right] = \sin\left( \frac{\pi}{2} + \frac{\pi}{3} \right)$
 
$\sin\left( \frac{3\pi + 2\pi}{6} \right) = \sin\left( \frac{5\pi}{6} \right)$
 
$\sin\left( \frac{5\pi}{6} \right) = \frac{1}{2}$