Question

$co{s}^{-1}\left(cos\frac{7\pi }{6}\right)=$

• A.
• B.
• C.
• D. None of these

Answer 1

The correct option is B

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