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Question: Answered & Verified by Expert
If $f(t)=\int_{-t}^t \frac{d x}{1+x^2}$, then $f^{\prime}(1)$ is
MathematicsDefinite IntegrationJEE Main
Options:
  • A Zero
  • B $2 / 3$
  • C -1
  • D 1
Solution:
1118 Upvotes Verified Answer
The correct answer is: 1
Given $f(t)=\int_t^t \frac{d x}{1+x^2}=\left[\tan ^{-1} x\right]_{-t}^t=2 \tan ^{-1} t$
Differentiating with respect to $t, \quad f^{\prime}(t)=\frac{2}{1+t^2}$
$\Rightarrow \quad f^{\prime}(1)=\frac{2}{2}=1$

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