MCQ
If $0 < x < 1$, then ${\cot ^{ - 1}}\left( {\frac{{2{x^2} - 1}}{{2x\sqrt {1 - {x^2}} }}} \right)$ is equal to
- A$ - 2{\cot ^{ - 1}}x$
- B$\pi - 2{\cos ^{ - 1}}x$
- ✓$ 2{\cos ^{ - 1}}x$
- D$2{\cos ^{ - 1}}x - \pi$
put $x = \cos \theta $ $\because $ $\theta \in \left( {0,\frac{\pi }{2}} \right)\quad \therefore \quad 0 < x < 1$
$\Rightarrow \quad \cot ^{-1}\left(\frac{\cos 2 \theta}{2 \cos \theta|\sin \theta|}\right)$
$=\cot ^{-1}(\cot 2 \theta)=2 \theta=2 \cos ^{-1} x$
$\because 2 \theta \in(0, \pi)$
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