Mathematics · Limits, Continuity and Differentiability

JEE Main 2026 — 24 January, Morning Shift — Question 1

If the function f(x)=ex(etan⁡x−x−1)+log⁡e(sec⁡x+tan⁡x)−xtan⁡x−x\mathrm{f}(\mathrm{x}) =\frac{\mathrm{e}^{\mathrm{x}}\left(\mathrm{e}^{\tan \mathrm{x}-\mathrm{x}}-1\right)+\log _{\mathrm{e}}(\sec \mathrm{x}+\tan \mathrm{x})-\mathrm{x}}{\tan \mathrm{x}-\mathrm{x}} is Continuous at x=0\mathrm{x}=0, then the value of f(0)\mathrm{f}(0) is equal to

  1. Option A:

    22

  2. Option B:

    23\frac{2}{3}

  3. Option C:

    12\frac{1}{2}

  4. Option D:

    32\frac{3}{2}

    Correct

Answer: D

Step-by-step solution

f(0)=Lim⁡x→0etan⁡x−ex+ln⁡(sec⁡x+tan⁡x)−xtan⁡x−x\mathrm{f}(0)=\underset{\mathrm{x} \rightarrow 0}{\operatorname{Lim}} \frac{\mathrm{e}^{\tan \mathrm{x}}-\mathrm{e}^{\mathrm{x}}+\ln (\sec \mathrm{x}+\tan \mathrm{x})-\mathrm{x}}{\tan \mathrm{x}-\mathrm{x}}

Applying L'hospital rule

⇒f(0)=Lim⁡x→0etan⁡x⋅sec⁡2x−ex+sec⁡x−1sec⁡2x−1\Rightarrow \mathrm{f}(0)=\operatorname{Lim}_{\mathrm{x} \rightarrow 0} \frac{\mathrm{e}^{\tan \mathrm{x}} \cdot \sec ^{2} \mathrm{x}-\mathrm{e}^{\mathrm{x}}+\sec \mathrm{x}-1}{\sec ^{2} \mathrm{x}-1}

⇒f(0)=Lim⁡x→0etan⁡x(sec⁡2x−1)+(etan⁡x−ex)+sec⁡x−1tan⁡2x\Rightarrow \mathrm{f}(0)=\operatorname{Lim}_{\mathrm{x} \rightarrow 0} \frac{\mathrm{e}^{\tan \mathrm{x}}\left(\sec ^{2} \mathrm{x}-1\right)+\left(\mathrm{e}^{\tan \mathrm{x}}-\mathrm{e}^{\mathrm{x}}\right)+\sec \mathrm{x}-1}{\tan ^{2} \mathrm{x}}

⇒f(0)=Lim⁡x→0(etan⁡x+ex(etan⁡x−x−1)tan⁡2x+1sec⁡x+1)\Rightarrow f(0)=\operatorname{Lim}_{x \rightarrow 0}\left(e^{\tan x}+\frac{e^{x}\left(e^{\tan x-x}-1\right)}{\tan ^{2} x}+\frac{1}{\sec x+1}\right)

⇒f(0)=1+0+12=32\Rightarrow \mathrm{f}(0)=1+0+\frac{1}{2}=\frac{3}{2}

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Limits, Continuity and Differentiability
Topic
Continuity