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Question #41524

Difficulty: 8/10 | 🟢 Free

The Question

Evaluate the integral: I=∫0πln⁡∣3sin⁡x−cos⁡x∣sin⁡2x dxI = \int_{0}^{\pi} \ln|\sqrt{3}\sin x - \cos x| \sin 2x \, dx

Options

  • A.

    −3π4-\frac{\sqrt{3}\pi}{4}

  • B.

    −π4-\frac{\pi}{4}

  • C.

    3π4\frac{\sqrt{3}\pi}{4}

  • D.

    00

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Monster

Ultra-high difficulty questions designed to test your limit, stamina, and deep conceptual understanding.

Concepts Behind This Question

Logarithmic Integration via Trig Manipulation|Definite Integral Properties (King's Property)|Modulus Inequality Logic|Non-Differentiable Extrema

Why This Question Is Tricky

Common Mistakes

This question tests the integration of logarithmic trigonometric functions combined with definite integral properties.

The primary trap is the modulus inside the logarithm.

Students often ignore the modulus, leading to domain errors since 3sin⁡x−cos⁡x\sqrt{3}\sin x - \cos x is negative on [0,π/6)[0, \pi/6).

The non-differentiable extremum at x=π/6x = \pi/6 forces the use of the modulus.

The elegant solution bypasses a messy split-interval integration by recognizing that after a phase shift, the integrand becomes periodic with period π\pi.

This allows shifting the integration bounds to [0,π][0, \pi], where the sine function is positive, naturally resolving the modulus and setting up a clean application of King's Property and integration by parts.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterIntegrals - Class 12
ConceptLogarithmic Integration via Trig Manipulation
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree