If $\sin ^{-1}\left(\frac{x}{13}\right)+\operatorname{cosec}^{-1}\left(\frac{13}{12}\right)=\frac{\pi}{2}$,…

If $\sin ^{-1}\left(\frac{x}{13}\right)+\operatorname{cosec}^{-1}\left(\frac{13}{12}\right)=\frac{\pi}{2}$, then the value of $x$ is
  1. 4
  2. 12
  3. 5
  4. 11

Solution

$\begin{aligned} & \sin ^{-1}\left(\frac{x}{13}\right)=\frac{\pi}{2}-\operatorname{cosec}^{-1}\left(\frac{13}{12}\right) \\ & =\sec ^{-1}\left(\frac{13}{12}\right)=\cos ^{-1}\left(\frac{12}{13}\right) \\ & \therefore \quad \sin ^{-1}\left(\frac{x}{13}\right)=\sin ^{-1}\left(\frac{5}{13}\right) \\ & \therefore \quad x=5 \end{aligned}$

Asked in: MHT CET 2024 (15 May Shift 2)

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