Question bank/JEE Main/Mathematics

JEE MainMathematicsModerateDefinite Integration

If
integral 
∫24\mspace2mux2−4x4dx=ln(2+3)−λ364,\int_{2}^{4}\mspace{2mu}\sqrt{\frac{x^{2} - 4}{x^{4}}}dx = ln(2 + \sqrt{3}) - \frac{\lambda\sqrt{3}}{64}, then
find the value of 
λ\lambda. \

Show answer and solution
∫24\mspace2mux2−4x4\int_{2}^{4}\mspace{2mu}\sqrt{\frac{x^{2} - 4}{x^{4}}}
dx Put x = 2
sec⁡θ\sec\theta
dx =
2sec⁡θtan⁡θdθ2\sec\theta\tan\theta d\theta
=∫0π/3\mspace2mu2tanθ4sec⁡2θ⋅2sec⁡θtan⁡θdθ= \int_{0}^{\pi/3}\mspace{2mu}\frac{2tan\theta}{4\sec^{2}\theta} \cdot 2\sec\theta\tan\theta d\theta
=∫0π3\mspace2musin⁡2θcos⁡θdθ=∫0π3\mspace2mu(sec⁡θ−cos⁡θ)dθ= \int_{0}^{\frac{\pi}{3}}\mspace{2mu}\frac{\sin^{2}\theta}{\cos\theta}d\theta = \int_{0}^{\frac{\pi}{3}}\mspace{2mu}\left( \sec\theta - \cos\theta \right)d\theta
=ln(secθ+tanθ)0π/3−(sinθ)0π/3\mathcal{= l}n(sec\theta + tan\theta)_{0}^{\pi/3} - (sin\theta)_{0}^{\pi/3}
=ln(2+3)−32= ln(2 + \sqrt{3}) - \frac{\sqrt{3}}{2}.

Source: Grass-G / M-13 Mathematics Paper 4 Nov.docx

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