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COMEDK · Maths · 28. Indefinite Integration

\(\int e^{x}(\cos x-\sin x) d x\) is equal to

  1. A \(e^{x} \cos x+C\)
  2. B \(e^{x} \sin x+C\)
  3. C \(-e^{x} \cos x+C\)
  4. D \(-e^{x} \sin x+C\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(e^{x} \cos x+C\)

Step-by-step Solution

Detailed explanation

\begin{aligned} \text{Let} \quad I &=\int e^{x}(\cos x-\sin x) d x \\ &=\int e^{x} \cos x d x-\int e^{x} \sin x d x \\ &=\int e^{x} \cos x d x-\left[e^{x}(-\cos x)-\int e^{x}(-\cos x) d x\right] \\ &=\int e^{x} \cos x d x+e^{x} \cos x-\int e^{x} \cos x d x \\ &=e^{x} \cos x+C…