MCQ
$\lim _{x \rightarrow 0} \frac{\sin x}{\sqrt{x+1}-\sqrt{1-x}}$ is equal to
  • $1$
  • B
    $0$
  • C
    $2$
  • D
    $-1$

Answer

Correct option: A.
$1$
Given, $\lim _{x \rightarrow 0} \frac{\sin x}{\sqrt{x+1}-\sqrt{1-x}}$
$=\lim _{x \rightarrow 0} \frac{\sin x[\sqrt{x+1}+\sqrt{1-x}]}{(\sqrt{x+1}-\sqrt{1-x}) \cdot(\sqrt{x+1}+\sqrt{1-x})}$
$=\lim _{x \rightarrow 0} \frac{\sin x[\sqrt{x+1}+\sqrt{1-x}]}{x+1-1+x}$
$=\lim _{x \rightarrow 0} \frac{\sin x[\sqrt{x+1}+\sqrt{1-x}]}{2 x}$
$=\frac{1}{2} \cdot \lim _{x \rightarrow 0} \frac{\sin x}{x}[\sqrt{x+1}+\sqrt{1-x}]$
Taking limits, we get
$=\frac{1}{2} \times 1 \times[\sqrt{0+1}+\sqrt{1-0}]$
$=\frac{1}{2} \times 1 \times 2$
$=1$

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