MCQ
If $y = {\log _2}[{\log _2}(x)]$, then ${{dy} \over {dx}}$ is equal to
  • ${{{{\log }_2}e} \over {x{{\log }_e}x}}$
  • B
    ${1 \over {{{\log }_e}x{{\log }_e}2}}$
  • C
    ${1 \over {{{\log }_e}{{(2x)}^x}}}$
  • D
    None of these

Answer

Correct option: A.
${{{{\log }_2}e} \over {x{{\log }_e}x}}$
a
(a) $y = {\log _2}[{\log _2}(x)] = {\log _e}({\log _e}x.{\log _2}e).{\log _2}e$

$ = [{\log _e}{\log _e}x + {\log _e}({\log _2}e)]{\log _2}e$

$\therefore \frac{{dy}}{{dx}} = {\log _2}e.\frac{1}{{x{{\log }_e}x}}$.

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