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CBSE Class 12 Mathematics 2026 Main Paper 65(B) · Q293 Marksdefinite_integral_symmetry

CBSE Class 12 Mathematics 2026 Main Paper 65(B) · Question 29 (Integrals)

Evaluate \(\int_0^\pi x\,dx/(1+\sin x)\).

✅ Step-by-Step Solution

Final Answer: π.
  1. The factor 1/(1+sin x) is invariant under x↦π−x.
  2. Thus the integral is (π/2) times J=∫₀^π dx/(1+sin x). Using t=tan(x/2), J=∫₀^∞2dt/(t+1)²=2.
  3. Multiply to obtain π.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] The factor 1/(1+sin x) is invariant under x↦π−x.
  • [2 marks] Thus the integral is (π/2) times J=∫₀^π dx/(1+sin x). Using t=tan(x/2), J=∫₀^∞2dt/(t+1)²=2.
  • [0.5 marks] Multiply to obtain π.

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