Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 12 - Vector-Valued Functions - 12.2 Exercises - Page 831: 55

Answer

$$\int_{0}^{2}\left( t \ \mathbf{i}+e^{t} \mathbf{j}-t e^{t} \mathbf{k}\right) d t =2 \ \mathbf{i}+\left(e^{2}-1\right) \mathbf{j}-\left(e^{2}+1\right) \mathbf{k}$$

Work Step by Step

Given $$\int_{0}^{2}\left(\mathrm{ti}+e^{t} \mathbf{j}-t e^{t} \mathbf{k}\right) d t $$ First, to find $$\int t e^t dt$$ let $u=t, du=dt $ and $dv=e^t dt, v=e^t$ so, we get $$\int t e^t dt=uv-\int v du=t e^t-\int e^t dt\\=t e^t- e^t =(t -1)e^t$$ Secondly, by integrating on a component-by-component basis produces \begin{align} I&=\int_{0}^{2}\left(\mathrm{ti}+e^{t} \mathbf{j}-t e^{t} \mathbf{k}\right) d t\\ &=\left[\frac{t^{2}}{2} \mathbf{i}\right]_{0}^{2}+\left[e^{t} \mathbf{j}\right]_{0}^{2}-\left[(t-1) \mathbf{e}^{t} \mathbf{k}\right]_{0}^{2}\\ &=2 \mathbf{i}+\left(e^{2}-e^0\right) \mathbf{j}-\left(e^{2}-1(-1)\right) \mathbf{k}\\ &=2 \mathbf{i}+\left(e^{2}-1\right) \mathbf{j}-\left(e^{2}+1\right) \mathbf{k} \end{align}
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