MCQ
${d \over {dx}}{\cos ^{ - 1}}{{x - {x^{ - 1}}} \over {x + {x^{ - 1}}}} =$
- A${1 \over {1 + {x^2}}}$
- B${{ - 1} \over {1 + {x^2}}}$
- C${2 \over {1 + {x^2}}}$
- ✓${{ - 2} \over {1 + {x^2}}}$
$y = {\cos ^{ - 1}}\left( {\frac{{x - {x^{ - 1}}}}{{x + {x^{ - 1}}}}} \right) = {\cos ^{ - 1}}\left( {\frac{{{x^2} - 1}}{{{x^2} + 1}}} \right)$
$ = {\cos ^{ - 1}}(\cos 2\theta ) = 2\theta $
$\Rightarrow \frac{{dy}}{{dx}} = \frac{{ - 2}}{{1 + {x^2}}}$.
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