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Class 12 Integrals · Long Answer3 Marksimproper_integral_divergence

Class 12 Maths · Integrals · Long Answer #171

Evaluate as an improper integral, or establish divergence: \(\int_{-\pi/2}^{\pi/2}e^{2x}(1-\sin2x)/(1-\cos2x)dx\).

✅ Step-by-Step Solution

Final Answer: Diverges to +∞.
  1. The denominator vanishes at the interior point x=0. Any improper integral must be split into separate one-sided integrals there.
  2. As x→0, e^(2x)→1, 1−sin2x→1 and 1−cos2x∼2x². Thus the integrand is asymptotic to 1/(2x²)>0.
  3. The integral of 1/x² diverges at 0, so comparison shows both one-sided contributions diverge to +∞.
  4. The stated improper integral therefore diverges to +∞; it has no finite value.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] The denominator vanishes at the interior point x=0. Any improper integral must be split into separate one-sided integrals there.
  • [1 mark] As x→0, e^(2x)→1, 1−sin2x→1 and 1−cos2x∼2x². Thus the integrand is asymptotic to 1/(2x²)>0.
  • [1 mark] The integral of 1/x² diverges at 0, so comparison shows both one-sided contributions diverge to +∞.
  • [0.5 marks] The stated improper integral therefore diverges to +∞; it has no finite value.

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