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JEE Advanced 2025 · Integrals

If α=∫122tan⁡−1x2x2−3x+2 dx\alpha = \int_{\frac{1}{2}}^{2} \frac{\tan^{-1} x}{2x^{2} - 3x + 2}\,dx, then the value of 7tan⁡(2α7π)\sqrt{7}\tan\left(\frac{2\alpha\sqrt{7}}{\pi}\right) is ________. (Here, the inverse trigonometric function tan⁡−1x\tan^{-1} x assumes values in (−π2,π2)\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)).

Answer: 2121

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If α = ∫_(1/2)² (tan⁻¹ x)/(2x² - 3x + 2) dx, then the value of √7tan(2α√7/π) is ________. (Here, the inverse trigonometric function tan⁻¹ x assumes values in (-π/2, π/2)). α=∫1/22tan⁡−1x2x2−3x+2 dx\alpha = \int_{1/2}^{2} \frac{\tan^{-1} x}{2x^2 - 3x + 2}\,dx tan⁡−1x∈(−π2,π2)\tan^{-1} x \in \left(-\frac{\pi}{2}, \frac{\pi}{2}\right) Find: 7tan⁡ ⁣(2α7π)\text{Find: } \sqrt{7}\tan\!\left(\frac{2\alpha\sqrt{7}}{\pi}\right) x=1t⇒2x2−3x+2=2t2−3t+2t2x = \frac{1}{t} \Rightarrow 2x^2-3x+2 = \frac{2t^2-3t+2}{t^2} I=∫1/22tan⁡−11x2x2−3x+2 dxI = \int_{1/2}^{2} \frac{\tan^{-1}\frac{1}{x}}{2x^2-3x+2}\,dx 2I=∫1/22tan⁡−1x+tan⁡−11x2x2−3x+2 dx2I = \int_{1/2}^{2} \frac{\tan^{-1} x + \tan^{-1}\frac{1}{x}}{2x^2-3x+2}\,dx tan⁡−1x+tan⁡−11x=π2(x>0)\tan^{-1} x + \tan^{-1}\frac{1}{x} = \frac{\pi}{2} \quad (x > 0) 2I=π2∫1/22dx2x2−3x+22I = \frac{\pi}{2}\int_{1/2}^{2} \frac{dx}{2x^2-3x+2} I=π4∫1/22dx2x2−3x+2I = \frac{\pi}{4}\int_{1/2}^{2} \frac{dx}{2x^2-3x+2} 2x2−3x+2=2[(x−34)2+716]2x^2-3x+2 = 2\left[\left(x-\frac{3}{4}\right)^2 + \frac{7}{16}\right] ∫dx2x2−3x+2=27[tan⁡−14x−37]1/22\int\frac{dx}{2x^2-3x+2} = \frac{2}{\sqrt{7}}\left[\tan^{-1}\frac{4x-3}{\sqrt{7}}\right]_{1/2}^{2} =27[tan⁡−157+tan⁡−117]= \frac{2}{\sqrt{7}}\left[\tan^{-1}\frac{5}{\sqrt{7}} + \tan^{-1}\frac{1}{\sqrt{7}}\right] tan⁡−157+tan⁡−117=tan⁡−1(37)\tan^{-1}\frac{5}{\sqrt{7}} + \tan^{-1}\frac{1}{\sqrt{7}} = \tan^{-1}(3\sqrt{7}) I=α=π4⋅27tan⁡−1(37)=π27tan⁡−1(37)I = \alpha = \frac{\pi}{4}\cdot\frac{2}{\sqrt{7}}\tan^{-1}(3\sqrt{7}) = \frac{\pi}{2\sqrt{7}}\tan^{-1}(3\sqrt{7}) 2α7π=tan⁡−1(37)\frac{2\alpha\sqrt{7}}{\pi} = \tan^{-1}(3\sqrt{7}) 7tan⁡ ⁣(2α7π)=7⋅37=21\sqrt{7}\tan\!\left(\frac{2\alpha\sqrt{7}}{\pi}\right) = \sqrt{7}\cdot 3\sqrt{7} = 21

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