If $\tan ^{-1}\left(\frac{1-x}{1+x}\right)-\frac{1}{2} \tan ^{-1} x=0$, for $x>0$, then $x=$

If $\tan ^{-1}\left(\frac{1-x}{1+x}\right)-\frac{1}{2} \tan ^{-1} x=0$, for $x>0$, then $x=$
  1. $\sqrt{3}$
  2. $\frac{1}{\sqrt{2}}$
  3. $\frac{1}{\sqrt{3}}$
  4. $\frac{1}{3}$

Solution

Here $\tan ^{-1}\left(\frac{1-x}{1+x}\right)=\frac{1}{2} \tan ^{-1} x \Rightarrow \tan ^{-1}\left[\frac{1-x}{1+(1)(x)}\right]=\frac{1}{2} \tan ^{-1} x$ $\therefore \tan ^{-1}(1)-\tan ^{-1} x=\frac{1}{2} \tan ^{-1} x$ $\frac{\pi}{4}=\frac{3}{2} \tan ^{-1} x \Rightarrow \tan ^{-1} x=\frac{\pi}{4} \times \frac{2}{3} \Rightarrow \tan ^{-1} x=\frac{\pi}{6}$ $\therefore x=\tan \frac{\pi}{6}=\frac{1}{\sqrt{3}}$

Asked in: MHT CET 2020 (13 Oct Shift 1)

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