MHT CET · Maths · Inverse Trigonometric Functions

Considering only the Principal values of inverse function, the set
\(
\left\{x \geq 0 / \tan ^{-1}(2 x)+\tan ^{-1} 3 x=\frac{\pi}{4}\right\}
\)

A is a singleton set.
B contains more than two elements.
C contains two elements.
D is an empty set.

Verified Solution

Answer & Solution

Correct Answer

(A) is a singleton set.

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \tan ^{-1}(2 x)+\tan ^{-1}(3 x)=\frac{\pi}{4} \\ & \Rightarrow \tan ^{-1} \frac{2 x+3 x}{1-2 x \times 3 x}=\tan ^{-1}(1) \\ & \Rightarrow \frac{5 x}{1-6 x^2}=1 \\ & \Rightarrow 5 x=1-6 x^2 \\ & \Rightarrow 6 x^2+5 x-1=0 \\ & \Rightarrow(x+1)(6 x-1)=0\end{aligned}\)
\(\Rightarrow x=-1\) or \(x=\frac{1}{6}\)
But \(x \geq 0\)
Hence \(x=\frac{1}{6}\) (only) i.e., single ton set

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Considering only the Principal values of inverse function, the set\(\left\{x \geq 0 / \tan ^{-1}(2 x)+\tan ^{-1} 3 x=\frac{\pi}{4}\right\}\)

Step-by-step Solution

Considering only the Principal values of inverse function, the set
\(
\left\{x \geq 0 / \tan ^{-1}(2 x)+\tan ^{-1} 3 x=\frac{\pi}{4}\right\}
\)