Question:medium

$\int_0^1 \tan^{-1} x \, dx = $ ______.

Show Hint

Whenever you have to integrate a lone logarithmic ($\ln x$) or inverse trig function ($\sin^{-1} x$, $\tan^{-1} x$), ALWAYS multiply it by 1 and use Integration by Parts!
Updated On: Jun 19, 2026
  • $\pi/4 - \log 2$
  • $\pi/4 - \log \sqrt{2}$
  • $\pi/4 + \log 2$
  • $\pi/4 + \log \sqrt{2}$
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Understanding the Concept:
Integrate using Integration by Parts (ILATE rule): $\int u \cdot v \, dx = u \int v \, dx - \int (u' \int v \, dx) dx$.

Step 2: Formula Application:

Let $u = \tan^{-1} x$ and $v = 1$. $\int \tan^{-1} x \cdot 1 \, dx = x \tan^{-1} x - \int \frac{x}{1+x^2} \, dx$.

Step 3: Explanation:

The integral $\int \frac{x}{1+x^2} \, dx$ is $\frac{1}{2} \log(1+x^2)$. Applying limits $[0, 1]$: $[x \tan^{-1} x - \frac{1}{2} \log(1+x^2)]_0^1$ $= (1 \cdot \frac{\pi}{4} - \frac{1}{2} \log 2) - (0 - 0)$ $= \frac{\pi}{4} - \log(2^{1/2}) = \frac{\pi}{4} - \log \sqrt{2}$.

Step 4: Final Answer:

The integral is $\pi/4 - \log \sqrt{2}$.
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