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JEE Main 202528 JanuaryMorning Shift
Exam
JEE Main
Year
2025
Date
28 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Definite Integration

JEE Main 2025 · 28 January · Morning Shift · Mathematics · Definite Integration

If ∫_ -(π)/(2) ^ (π)/(2) (96 x^2 ^2 x)/((1+e^x)) d x=π(α π^2+β), α,...

If ∫−π2π296x2cos⁡2x(1+ex)dx=π(απ2+β),α,β∈Z\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \frac{96 x^2 \cos ^2 x}{\left(1+e^x\right)} \mathrm{d} x=\pi\left(\alpha \pi^2+\beta\right), \alpha, \beta \in \mathbb{Z}, then (α+β)2(\alpha+\beta)^2 equals

Options

  1. A64
  2. B196
  3. C144
  4. D100

Correct answer

D. 100

Step-by-step solution

I=∫0π296x2cos⁡2x1+exdx2I=2∫0π296x2cos⁡2xdxI=96∫0π2x2cos⁡2xdx=48∫0π2x2(1+cos⁡2x)dx=2π2+48(0−0)−48∫0π2xsin⁡2xdx=2π2−12π+[0−0]=π(2π2−12)=π(απ2+β)⇒(α+β)2=100\begin{aligned} & I=\int_0^{\frac{\pi}{2}} \frac{96 x^2 \cos ^2 x}{1+e^x} d x \\ & 2 I=2 \int_0^{\frac{\pi}{2}} 96 x^2 \cos ^2 x d x \\ & I=96 \int_0^{\frac{\pi}{2}} x^2 \cos ^2 x d x \\ & =48 \int_0^{\frac{\pi}{2}} x^2(1+\cos 2 x) d x \\ & =2 \pi^2+48(0-0)-48 \int_0^{\frac{\pi}{2}} x \sin 2 x d x \\ & =2 \pi^2-12 \pi+[0-0]=\pi\left(2 \pi^2-12\right) \\ & =\pi\left(\alpha \pi^2+\beta\right) \\ & \Rightarrow(\alpha+\beta)^2=100\end{aligned}
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