If $\tan ^{-1}(2 x)+\tan ^{-1}(3 x)=\frac{\pi}{4}$, where $x>0$, then $x=$

If $\tan ^{-1}(2 x)+\tan ^{-1}(3 x)=\frac{\pi}{4}$, where $x>0$, then $x=$
  1. 1
  2. $\frac{1}{6}$
  3. $\frac{1}{3}$
  4. $\frac{1}{2}$

Solution

$\begin{aligned} & \tan ^{-1}(2 x)+\tan ^{-1}(3 x)=\frac{\pi}{4} \\ & \therefore \tan ^{-1}\left[\frac{2 x+3 x}{1-(2 x)(3 x)}\right]=\frac{\pi}{4} \Rightarrow \tan \frac{\pi}{4}=\frac{5 x}{1-6 x^2}=1 \\ & \therefore 6 x^2+5 x-1=0 \Rightarrow(6 x-1)(x+1)=0 \Rightarrow x=-1, \frac{1}{6} \end{aligned}$ Since $x>0$, we get $x=\frac{1}{6}$

Asked in: MHT CET 2021 (24 Sep Shift 1)

Practice more Inverse Trigonometric Functions questions on Aicharya