Inverse Trigonometric Functions Question - CBSE

Question

The principal value of $\cos^{-1}\left(\cos \dfrac{7\pi}{6}\right)$ is:
(a) $\dfrac{5\pi}{6}$
(b) $\dfrac{7\pi}{6}$
(c) $\dfrac{\pi}{6}$
(d) $-\dfrac{\pi}{6}$

Accepted Answer

$\cos(7\pi/6) = \cos(5\pi/6) \Rightarrow \cos^{-1}(\cos(5\pi/6)) = 5\pi/6$. [1.0 Mark]

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🎯 Official CBSE Marking Scheme:
Evaluating principal value $= 5\pi/6$: 1.0 Mark

Question:

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