MCQ
${d \over {dx}}{\cos ^{ - 1}}\sqrt {{{1 + {x^2}} \over 2}} = $
  • A
    ${{ - 1} \over {2\sqrt {1 - {x^4}} }}$
  • B
    ${1 \over {2\sqrt {1 - {x^4}} }}$
  • ${{ - x} \over {\sqrt {1 - {x^4}} }}$
  • D
    ${x \over {\sqrt {1 - {x^4}} }}$

Answer

Correct option: C.
${{ - x} \over {\sqrt {1 - {x^4}} }}$
c
(c) Putting ${x^2} = \cos 2\theta $, we have

$\frac{d}{{dx}}\left[ {{{\cos }^{ - 1}}\sqrt {\frac{{1 + {x^2}}}{2}} } \right] = \frac{d}{{dx}}[{\cos ^{ - 1}}\cos \theta ]$

$ = \frac{d}{{dx}}[\theta ] = \frac{d}{{dx}}\left[ {\frac{1}{2}{{\cos }^{ - 1}}{x^2}} \right] = \frac{{ - x}}{{\sqrt {1 - {x^4}} }}$.

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