Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 8 - Techniques of Integration - 8.1 Integration by Parts - Exercises - Page 395: 55

Answer

$$\frac{e^{\pi}+1}{2}$$

Work Step by Step

Given $$\int_{0}^{\pi} e^{x} \sin x d x$$ \begin{align*} u &= \sin x \ \ \ \ \ \ \ \ \ dv= e^xdx\\ du &= \cos x dx \ \ \ \ \ \ \ \ v= e^x \end{align*} Then, \begin{align*} \int \sin x e^{x} d x &=(\sin x)\left(e^{x}\right)-\int e^{x} \cos x d x \\ &=e^{x} \sin x- \int \cos x e^{x} d x \end{align*} For the integral part again, let \begin{align*} u &= \cos x\ \ \ \ \ \ \ \ \ dv= e^xdx\\ du &= -\sin xdx \ \ \ \ \ \ \ \ v= e^x \end{align*}Then, \begin{align*} \int \sin x e^{x} d x&=e^{x} \sin x- \left(e^{x} \cos x+ \int e^{x} \sin x d x\right)\\ \int \sin x e^{x} d x&=e^{x} \sin x- e^{x} \cos x- \int e^{x} \sin x d x\\ 2 \int \sin x e^{x} d x&=e^{x} \sin x- e^{x} \cos x\\ \int \sin 2 x e^{x} d x&=\frac{1}{2} e^{x}(\sin x- \cos x) +C\\ \int _{0}^{\pi}\sin 2 x e^{x} d x&=\frac{1}{2} e^{x}(\sin x- \cos x) \bigg|_{0}^{\pi}\\ &= \frac{e^{\pi}+1}{2} \end{align*}
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