Class CBSE Class 12 Mathematics Definite Integrals Q #1818
COMPETENCY BASED
APPLY
5 Marks 2026 AISSCE(Board Exam) LA
Evaluate: $\int_{0}^{1}\frac{x~\tan^{-1}x}{(1+x^{2})^{3/2}}dx$

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Detailed Solution

Step 1: Substitution

Let $x = \tan \theta$. Then $dx = \sec^2 \theta d\theta$. When $x=0, \theta=0$ and when $x=1, \theta=\frac{\pi}{4}$. The integral becomes: $$I = \int_{0}^{\pi/4} \frac{\tan \theta \cdot \theta}{(\sec^2 \theta)^{3/2}} \cdot \sec^2 \theta d\theta = \int_{0}^{\pi/4} \frac{\theta \tan \theta}{\sec^3 \theta} \cdot \sec^2 \theta d\theta = \int_{0}^{\pi/4} \theta \sin \theta d\theta$$

Step 2: Integration by Parts

Using the formula $\int u dv = uv - \int v du$, let $u = \theta$ and $dv = \sin \theta d\theta$. Then $du = d\theta$ and $v = -\cos \theta$. $$I = [\theta(-\cos \theta)]_{0}^{\pi/4} - \int_{0}^{\pi/4} (-\cos \theta) d\theta$$

Step 3: Evaluation

$$I = [-\theta \cos \theta]_{0}^{\pi/4} + [\sin \theta]_{0}^{\pi/4}$$ $$I = (-\frac{\pi}{4} \cdot \frac{1}{\sqrt{2}} - 0) + (\frac{1}{\sqrt{2}} - 0) = \frac{1}{\sqrt{2}} - \frac{\pi}{4\sqrt{2}} = \frac{2-\pi}{4\sqrt{2}} = \frac{\sqrt{2}}{4} - \frac{\pi}{4\sqrt{2}}$$ Simplifying, we get $\frac{2-\pi}{4\sqrt{2}} = \frac{\sqrt{2}-\frac{\pi}{\sqrt{2}}}{4} = \frac{2-\pi}{4\sqrt{2}}$.

Final Answer: \frac{2-\pi}{4\sqrt{2}}

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to select and implement a specific trigonometric substitution followed by integration by parts to solve a complex definite integral.
Knowledge Dimension: PROCEDURAL
Justification: The problem relies on a sequence of algorithmic steps (substitution, simplification, and integration by parts) to reach the solution.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. This question tests the student's ability to handle advanced integration techniques beyond standard textbook formulas, aligning with the NEP 2020 focus on higher-order thinking skills.