Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 4 - Integrals - 4.5 The Substitution Rule - 4.5 Exercises - Page 347: 82



Work Step by Step

To evaluate the integral $$\int_0^1xe^{-x^2}dx$$ we will use substitution $-x^2=t$ which gives us $-2xdx=dt\Rightarrow xdx=-\frac{dt}{2}$. The integration bounds would be: for $x=0$ we have $t=0$ and for $x=1$ we have $t=-1$. Putting this into the integral we get: $$\int_0^1xe^{-x^2}dx=\int_0^{-1}e^t\Big(-\frac{dt}{2}\Big)=\frac{1}{2}\int_{-1}^0e^tdt=\frac{1}{2}\left.e^t\right|_{-1}^0=\frac{1}{2}(e^0-e^{-1})=\frac{1}{2}(1-\frac{1}{e})=\frac{e-1}{2e}$$
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