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JEE Advanced 2022Paper 1
Exam
JEE Advanced
Year
2022
Paper
Paper 1
Subject
Mathematics
Chapter
Limits

JEE Advanced 2022 · Paper 1 · Mathematics · Limits

Let α be a positive real number. Let f: ℝ → ℝ and g: (α, ∞) → ℝ be...

Let α\alpha be a positive real number. Let f:R→Rf: \mathbb{R} \to \mathbb{R} and g:(α,∞)→Rg: \left(\alpha, \infty\right) \to \mathbb{R} be the functions defined by f(x)=sin⁡(\pix12)f\left(x\right) = \sin \left(\dfrac{\pix}{12}\right) and g(x)=2log⁡e(x−α)log⁡e(ex−eα)g\left(x\right) = \dfrac{2\log_{e}\left(\sqrt{x} - \sqrt{\alpha}\right)}{\log_{e}\left({e}^{\sqrt{x}} - {e}^{\sqrt{\alpha}}\right)}.
Then the value of lim⁡x→α+f(g(x))\lim_{x \to {\alpha}^{+}}f\left(g\left(x\right)\right) is ______.

Correct answer

0

Step-by-step solution

lim⁡x→α+g(x)=lim⁡x→α+2log⁡e(x−α)log⁡e(ex−eα)=lim⁡x→α+2x−α(12x)1ex−eα(12xex)\lim_{x \to {\alpha}^{+}}g\left(x\right) = \lim_{x \to {\alpha}^{+}}\dfrac{2\log_{e}\left(\sqrt{x} - \sqrt{\alpha}\right)}{\log_{e}\left({e}^{\sqrt{x}} - {e}^{\sqrt{\alpha}}\right)} = \lim_{x \to {\alpha}^{+}}\dfrac{\dfrac{2}{\sqrt{x} - \sqrt{\alpha}}\left(\dfrac{1}{2\sqrt{x}}\right)}{\dfrac{1}{{e}^{\sqrt{x}} - {e}^{\sqrt{\alpha}}}\left(\dfrac{1}{2\sqrt{x}}{e}^{\sqrt{x}}\right)}

=lim⁡x→α+ex−eαx−α1ex⋅2= \lim_{x \to {\alpha}^{+}}\dfrac{{e}^{\sqrt{x}} - {e}^{\sqrt{\alpha}}}{\sqrt{x} - \sqrt{\alpha}}\dfrac{1}{{e}^{\sqrt{x}}} \cdot 2

=2eαlim⁡x→α+ex⋅12x12x=2= \dfrac{2}{{e}^{\sqrt{\alpha}}}\lim_{x \to {\alpha}^{+}}\dfrac{{e}^{\sqrt{x}} \cdot \dfrac{1}{2\sqrt{x}}}{\dfrac{1}{2\sqrt{x}}} = 2

lim⁡x→α+f(g(x))=f(lim⁡x→α+g(x))\lim_{x \to {\alpha}^{+}}f\left(g\left(x\right)\right) = f\left(\lim_{x \to {\alpha}^{+}}g\left(x\right)\right)

=f(2)=sinπ6=12=0.50= f\left(2\right) = sin\dfrac{\pi}{6} = \dfrac{1}{2} = 0 . 50

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