MCQ
$\lim _{x \rightarrow 0} \frac{x^3 \cot x}{1-\cos x}=$
  • A
    $0$
  • B
    1
  • 2
  • D
    -2

Answer

Correct option: C.
2
(C)
$\lim _{x \rightarrow 0} \frac{x^3 \cot x}{1-\cos x}=\lim _{x \rightarrow 0}\left(\frac{x^3 \cot x}{1-\cos x} \times \frac{1+\cos x}{1+\cos x}\right)$
$=\lim _{x \rightarrow 0} \frac{\left(x^3 \cot x\right)(1+\cos x)}{1-\cos ^2 x}$
$=\lim _{x \rightarrow 0} \frac{\left(x^3 \cot x\right)(1+\cos x)}{\sin ^2 x}$
$=\lim _{x \rightarrow 0}\left(\frac{x}{\sin x}\right)^3 \times \lim _{x \rightarrow 0} \cos x \times \lim _{x \rightarrow 0}(1+\cos x)$
$=(1)^3(1)(1+1)=2$

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