Q. If$\ y = \log^{n}{x,\ where\log^{n}{means\log{\log{\log{\ldots(repeated\ n\ times\ ),then}}}}}$ $x\log{x\log^{2}{x\log^{3}{x\ldots\log^{n - 1}{x\log^{n}x\frac{dy}{dx}\ }\ }}}$is equal to

A) $\log x$
B) $x$
C) $\frac{1}{\log x}$
D) $\log^{n}x$
Explanation

(d)
We have, $y = \log^{n}x$
Where $\log^{n}{means\log{\log{\ldots(repeated\ n\ times).}}}$
On differentiating w.r.t. $x,\$we get
$\ \frac{dy}{dx} = \frac{1}{x\log x\log^{2}{x\ldots\log^{n - 1}x}}$
$\therefore$ $x\log{x\log^{2}{x\ldots\log^{n - 1}{x\log^{n}{x\frac{dy}{dx}}}}}$
$= \frac{x\log{x\log^{2}{x\ldots\log^{n - 1}{x\log^{n}x}}}}{x\log{x\log^{2}{x\ldots\log^{n - 1}x}}} = \log^{n}x$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.