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If y=cot⁡−1(1−x1+x)y = \cot^{-1}\left(\frac{1-x}{1+x}\right) then dydx\frac{dy}{dx} equals

Solution

✅ Correct Option: 2

Since cot⁡−1u=π2−tan⁡−1u\cot^{-1}u = \frac{\pi}{2} - \tan^{-1}u and tan⁡−11−x1+x=π4−tan⁡−1x\tan^{-1}\frac{1-x}{1+x} = \frac{\pi}{4} - \tan^{-1}x, we get y=π4+tan⁡−1xy = \frac{\pi}{4} + \tan^{-1}x. Differentiating, dydx=11+x2\frac{dy}{dx} = \frac{1}{1+x^2}.

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