Q. If $\lim_{x \rightarrow 0}\frac{\left\lbrack (a - n)nx - \tan x \right\rbrack\sin{nx}}{x^{2}} = 0$, where $n$ is non-zero real number, then $a$ is equal to

A) 0
B) $\frac{n + 1}{n}$
C) $n$
D) $n + \frac{1}{n}$
Explanation

(d)
Given, $\lim_{x \rightarrow 0}\frac{\left\{ (a - n)nx - \tan x \right\}\sin{nx}}{x^{2}} = 0$
$\Rightarrow \ \ \ \ \ \ \lim_{x \rightarrow 0}{\left( (a - n)n - \frac{\tan x}{x} \right).}\frac{\sin{nx}}{x} = 0$
$\Rightarrow \ \ \ \ \ \ \ \ \left\lbrack \left\{ a - n \right\} n - 1 \right\rbrack n = 0$
$\Rightarrow \ \ \ \ \ \ \ \ \ a = n + \frac{1}{n}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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