MCQ
${d \over {dx}}{\tan ^{ - 1}}\left[ {{{\cos x - \sin x} \over {\cos x + \sin x}}} \right] = $
  • A
    ${1 \over {2\,\,(1 + {x^2})}}$
  • B
    ${1 \over {1 + {x^2}}}$
  • C
    $1$
  • $-1$

Answer

Correct option: D.
$-1$
d
(d) $\frac{d}{{dx}}{\tan ^{ - 1}}\left[ {\frac{{\cos x - \sin x}}{{\cos x + \sin x}}} \right]$

$ = \frac{d}{{dx}}{\tan ^{ - 1}}\left[ {\tan \left( {\frac{\pi }{4} - x} \right)} \right] = - 1$.

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