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COMEDK · Maths · 30. Definite Integration

\(\int_\limits0^{\dfrac{\pi}{2}} \dfrac{\cos x}{1+\cos x+\sin x} d x=\)

  1. A \(\dfrac{\pi}{4}+\dfrac{1}{2} \log 2\)
  2. B \(\dfrac{\pi}{4}-\log 2\)
  3. C \(\dfrac{\pi}{4}+\log 2\)
  4. D \(\dfrac{\pi}{4}-\dfrac{1}{2} \log 2\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\dfrac{\pi}{4}-\dfrac{1}{2} \log 2\)

Step-by-step Solution

Detailed explanation

Let \(I = \displaystyle\int_0^{\pi/2} \dfrac{\cos x}{1 + \cos x + \sin x}dx\) ... (1) Using \(\displaystyle\int_0^a f(x)dx = \int_0^a f(a-x)dx\), substitute \(x \to \dfrac{\pi}{2} - x\): \(I = \displaystyle\int_0^{\pi/2} \dfrac{\sin x}{1 + \sin x + \cos x}dx\) ... (2) Adding (1)…