MCQ
Find the principal values of: $\sec ^{-1}(2)$
  • A
    $\frac{\pi}{6}$
  • $\frac{\pi}{3}$
  • C
    $\frac{2 \pi}{3}$
  • D
    $\frac{5 \pi}{6}$

Answer

Correct option: B.
$\frac{\pi}{3}$
(b) : Let $\sec ^{-1}(2)=\theta \Rightarrow \sec \theta=2=\sec \frac{\pi}{3}$
$\Rightarrow \theta=\frac{\pi}{3} \in[0, \pi]-\left\{\frac{\pi}{2}\right\}$
$\therefore \quad$ Principal value of $\sec ^{-1}(2)$ is $\frac{\pi}{3}$.

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