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JEE Main 202430 JanuaryMorning Shift
Exam
JEE Main
Year
2024
Date
30 January
Shift
Morning Shift
Subject
Mathematics
Chapter
Limits

JEE Main 2024 · 30 January · Morning Shift · Mathematics · Limits

Let f: [- (π)/(2), (π)/(2)] → R be a differentiable function such...

Let f:[−π2,π2]→Rf: \left[- \dfrac{\pi}{2}, \dfrac{\pi}{2}\right] \to R be a differentiable function such that f(0)=12f\left(0\right) = \dfrac{1}{2}, If lim⁡x→0x∫0xf(t)dtex2−1=α\lim_{x \to 0}\dfrac{x{∫}_{0}^{x}f ( t ) dt}{{e}^{{x}^{2}} - 1} = \alpha, then 8α28{\alpha}^{2} is equal to :

Options

  1. A1616
  2. B22
  3. C11
  4. D44

Correct answer

B. 22

Step-by-step solution

Let, y=lim⁡x→0x∫0xf(t)dtex2−1y = \lim_{x \to 0}\dfrac{x{∫}_{0}^{x}f ( t ) dt}{{e}^{{x}^{2}} - 1}

⇒y=lim⁡x→0x∫0xf(t)dt(ex2−1x2)×x2⇒ y = \lim_{x \to 0}\dfrac{x{∫}_{0}^{x}f ( t ) dt}{\left(\dfrac{{e}^{{x}^{2}} - 1}{{x}^{2}}\right) \times {x}^{2}}

We know that, lim⁡x→0ex2−1x2=1\lim_{x \to 0}\dfrac{{e}^{{x}^{2}} - 1}{{x}^{2}} = 1

⇒y=lim⁡x→0∫0xf(t)dtx⇒ y = \lim_{x \to 0}\dfrac{{∫}_{0}^{x}f ( t ) dt}{x}

Applying L-hospital's rule and Newton Leibnitz Theorem we get,

⇒y=lim⁡x→0f(x)1⇒ y = \lim_{x \to 0}\dfrac{f ( x )}{1}

⇒y=f(0)⇒ y = f\left(0\right)

It is given that, f(0)=12f ( 0 ) = \dfrac{1}{2}

⇒y=12⇒ y = \dfrac{1}{2}

⇒α=12⇒ \alpha = \dfrac{1}{2}

⇒8α2=2⇒ 8{\alpha}^{2} = 2

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