MCQ
If ${\sin ^{ - 1}}x + {\sin ^{ - 1}}y = \frac{{2\pi }}{3},$ then ${\cos ^{ - 1}}x + {\cos ^{ - 1}}y = $
  • A
    $\frac{{2\pi }}{3}$
  • $\frac{\pi }{3}$
  • C
    $\frac{\pi }{6}$
  • D
    $\pi $

Answer

Correct option: B.
$\frac{\pi }{3}$
b
(b) ${\sin ^{ - 1}}x + {\sin ^{ - 1}}y = \frac{{2\pi }}{3}$

$ \Rightarrow \frac{\pi }{2} - {\cos ^{ - 1}}x + \frac{\pi }{2} - {\cos ^{ - 1}}y = \frac{{2\pi }}{3}$

==> ${\cos ^{ - 1}}x + {\cos ^{ - 1}}y = \pi - \frac{{2\pi }}{3} = \frac{\pi }{3}$.

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