Class CBSE Class 12 Mathematics Integrals Q #903
KNOWLEDGE BASED
APPLY
3 Marks 2023 SA
Evaluate $\int_{1}^{e}\frac{1}{\sqrt{4x^{2}-(x\log x)^{2}}}dx$

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Step-by-Step Solution

**Step 1: Simplify the integral** Let $I = \int_{1}^{e}\frac{1}{\sqrt{4x^{2}-(x\log x)^{2}}}dx = \int_{1}^{e}\frac{1}{\sqrt{x^2(4-(\log x)^{2})}}dx = \int_{1}^{e}\frac{1}{x\sqrt{4-(\log x)^{2}}}dx$
**Step 2: Apply substitution** Let $u = \log x$. Then, $\frac{du}{dx} = \frac{1}{x}$, so $du = \frac{1}{x}dx$. When $x = 1$, $u = \log 1 = 0$. When $x = e$, $u = \log e = 1$. Therefore, $I = \int_{0}^{1}\frac{1}{\sqrt{4-u^{2}}}du$
**Step 3: Evaluate the integral** We know that $\int \frac{1}{\sqrt{a^2 - x^2}} dx = \sin^{-1}(\frac{x}{a}) + C$. So, $I = \int_{0}^{1}\frac{1}{\sqrt{2^{2}-u^{2}}}du = \left[\sin^{-1}\left(\frac{u}{2}\right)\right]_{0}^{1} = \sin^{-1}\left(\frac{1}{2}\right) - \sin^{-1}(0)$
**Step 4: Find the final value** Since $\sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6}$ and $\sin^{-1}(0) = 0$, $I = \frac{\pi}{6} - 0 = \frac{\pi}{6}$

Correct Answer: π/6

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply the concepts of integration and substitution to solve the given definite integral. They must choose the appropriate substitution and manipulate the integral to find the solution.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure or algorithm to solve the integral, including choosing the correct substitution and applying the rules of integration.
Syllabus Audit: In the context of CBSE Class 12, this is classified as KNOWLEDGE. The question directly tests the student's knowledge and application of integration techniques covered in the textbook.