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CUET · MATHS · PYQ PAPER 2023

The value of \(\cos ^{-1}\left(\cos \frac{7 \pi}{6}\right)\) is:

  1. A \(\frac{7 \pi}{6}\)
  2. B \(\frac{5 \pi}{6}\)
  3. C \(\frac{\pi}{6}\)
  4. D \(\frac{\pi}{3}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{5 \pi}{6}\)

Step-by-step Solution

Detailed explanation

\(\cos \frac{7 \pi}{6} = \cos \left(\pi + \frac{\pi}{6}\right) = -\cos \frac{\pi}{6}\) \(\cos ^{-1}\left(-\cos \frac{\pi}{6}\right) = \cos ^{-1}\left(\cos \left(\pi - \frac{\pi}{6}\right)\right)\) \(\cos ^{-1}\left(\cos \frac{5 \pi}{6}\right) = \frac{5 \pi}{6}\)
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