Considering only the principal values of an inverse function, the set $\mathrm{A}=\left\{x \geq 0 / \tan…
Considering only the principal values of an inverse function, the set
$\mathrm{A}=\left\{x \geq 0 / \tan ^{-1} x+\tan ^{-1} 6 x=\frac{\pi}{4}\right\}$
- is an empty set.
- is a singleton set.
- contains more than two elements.
- contains two elements.
Solution
Consider, $\tan ^{-1} x+\tan ^{-1} 6 x=\frac{\pi}{4}$
$\begin{aligned}
& \Rightarrow \tan ^{-1}\left(\frac{7 x}{1-6 x^2}\right)=\frac{\pi}{4} \\
& \quad \quad \ldots\left[\tan ^{-1}(x)+\tan ^{-1}(y)=\tan ^{-1}\left(\frac{x+y}{1-x y}\right)\right] \\
& \Rightarrow \frac{7 x}{1-6 x^2}=1 \\
& \Rightarrow 7 x=1-6 x^2 \\
& \Rightarrow 6 x^2+7 x-1=0 \\
& \Rightarrow x=\frac{-7 \pm \sqrt{73}}{12} \\
& \quad \text { Since } x \geq 0 \\
& \therefore \quad x=\frac{-7+\sqrt{73}}{12}
\end{aligned}$
$\therefore \quad$ A is a singleton set.
Asked in: MHT CET 2023 (10 May Shift 1)
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