MCQ
Write the function in the simplest form: $\tan ^{-1} \frac{x}{\sqrt{a^{2}-x^{2}}},|x| < a$
  • A
    $\tan ^{-1} \frac{a}{x}$
  • B
    $\tan ^{-1} \frac{x}{a}$
  • C
    $\sin ^{-1} \frac{a}{x}$
  • $\sin ^{-1} \frac{x}{a}$

Answer

Correct option: D.
$\sin ^{-1} \frac{x}{a}$
d
$\tan ^{-1} \frac{x}{\sqrt{a^{2}-x^{2}}}$

Let, $x=a \sin \theta \Rightarrow \frac{x}{a}=\sin \theta \Rightarrow \sin ^{-1}\left(\frac{x}{a}\right)$

$\therefore \tan ^{-1} \frac{x}{\sqrt{a^{2}-x^{2}}}$

$=\tan ^{-1}\left(\frac{a \sin \theta}{\sqrt{a^{2}-a^{2} \sin ^{2} \theta}}\right)$

$=\tan ^{-1}\left(\frac{a \sin \theta}{a \sqrt{1-\sin ^{2} \theta}}\right)$

$=\tan ^{-1}\left(\frac{a \sin \theta}{a \cos \theta}\right)$

$=\tan ^{-1}(\tan \theta)=\theta=\sin ^{-1} \frac{x}{a}$

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