The value of $x$ such that $\sin \left(2 \tan ^{-1} \frac{3}{4}\right)=\cos \left(2 \tan ^{-1} x\right)$ is

The value of $x$ such that $\sin \left(2 \tan ^{-1} \frac{3}{4}\right)=\cos \left(2 \tan ^{-1} x\right)$ is
  1. 7
  2. $\frac{3}{7}$
  3. $\frac{1}{7}$
  4. $\frac{4}{7}$

Solution

$\begin{aligned} & \sin \left(2 \tan ^{-1} \frac{3}{4}\right)=\cos \left(2 \tan ^{-1} x\right) \\ & \Rightarrow \frac{2 \times \frac{3}{4}}{1+\left(\frac{3}{4}\right)^2}=\frac{1-x^2}{1+x^2}=\frac{24}{25} \\ & \Rightarrow 25-25 x^2=24+24 x^2 \Rightarrow 49 x^2=1 \Rightarrow x=\frac{1}{7}\end{aligned}$

Asked in: AP EAMCET 2024 (22 May Shift 1)

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