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Class 12 Integrals · Long Answer3 Marksdefinite_integration

Class 12 Maths · Integrals · Long Answer #87

Evaluate \(\int_0^{2\pi}dx/(1+e^{\sin x})\).

✅ Step-by-Step Solution

Final Answer: π
  1. Let I be the integral. Under reflection x↦2π−x, sin(2π−x)=−sin x.
  2. Thus I=∫₀^(2π)e^(sin x)/(1+e^(sin x))dx.
  3. Adding this to the original gives 2I=∫₀^(2π)1dx=2π.
  4. Therefore the integral equals π.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Let I be the integral. Under reflection x↦2π−x, sin(2π−x)=−sin x.
  • [1 mark] Thus I=∫₀^(2π)e^(sin x)/(1+e^(sin x))dx.
  • [1 mark] Adding this to the original gives 2I=∫₀^(2π)1dx=2π.
  • [0.5 marks] Therefore the integral equals π.

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