$\int_{0}^{\frac{\pi}{2}}\left(e^{\sin x}-e^{\cos x}\right) d x=$

$\int_{0}^{\frac{\pi}{2}}\left(e^{\sin x}-e^{\cos x}\right) d x=$
  1. $\frac{1}{2}$
  2. $0$
  3. $1$
  4. $\frac{\pi}{4}$

Solution

$\begin{aligned} \text {Let } I &=\int_{0}^{\frac{\pi}{2}}\left(e^{\sin x}-e^{\cos x}\right) d x ....(1)\\ &=\int_{0}^{\pi / 2} e^{\sin \left(\frac{\pi}{2}-x\right)}-e^{\cos \left(\frac{\pi}{2}-x\right)} \mathrm{dx} \\ &=\int_{0}^{\pi / 2} e^{\cos x}-e^{\sin x} d x....(2) \end{aligned}$ Adding equation (1) \& (2) we get $\begin{array}{l} 2 I=\int_{0}^{\pi / 2}\left(e^{\sin x}-e^{\cos x}-e^{\cos x}-e^{\sin x}\right) d x \\ 2 I=0 \Rightarrow I=0 \end{array}$

Asked in: MHT CET 2020 (15 Oct Shift 1)

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