Calculus (3rd Edition)

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

Chapter 16 - Multiple Integration - 16.2 Double Integrals over More General Regions - Exercises - Page 859: 32


The iterated integral after changing the order of integration is $\mathop \smallint \limits_0^2 \mathop \smallint \limits_0^{{y^2}} \sin {y^3}{\rm{d}}x{\rm{d}}y$ Evaluate: $\mathop \smallint \limits_{y = 0}^2 \mathop \smallint \limits_{x = 0}^{{y^2}} \sin {y^3}{\rm{d}}x{\rm{d}}y \simeq 0.3818$

Work Step by Step

We have $\mathop \smallint \limits_0^4 \mathop \smallint \limits_{\sqrt x }^2 \sin {y^3}{\rm{d}}y{\rm{d}}x$. From the limits of the integrals we obtain the domain description: ${\cal D} = \left\{ {\left( {x,y} \right)|0 \le x \le 4,\sqrt x \le y \le 2} \right\}$ Notice that this is a vertically simple region. Using this description we sketch the the domain of integration. Please see the figure attached. We change the order of integration such that the domain becomes a horizontally simple region. In this case, the lower and upper boundaries are $y=0$ and $y=2$, respectively. Whereas, the left boundary is $x=0$. To find the right boundary, we use $y = \sqrt x $ and get $x = {y^2}$. Thus, the new domain description: ${\cal D} = \left\{ {\left( {x,y} \right)|0 \le y \le 2,0 \le x \le {y^2}} \right\}$ So, the iterated integral after changing the order of integration is $\mathop \smallint \limits_0^2 \mathop \smallint \limits_0^{{y^2}} \sin {y^3}{\rm{d}}x{\rm{d}}y$ Next, we evaluate this integral: $\mathop \smallint \limits_{y = 0}^2 \mathop \smallint \limits_{x = 0}^{{y^2}} \sin {y^3}{\rm{d}}x{\rm{d}}y$ $ = \mathop \smallint \limits_{y = 0}^2 \sin {y^3}\left( {x|_0^{{y^2}}} \right){\rm{d}}y$ $ = \mathop \smallint \limits_{y = 0}^2 {y^2}\sin {y^3}{\rm{d}}y$ $ = - \frac{1}{3}\cos {y^3}|_0^2$ $ = - \frac{1}{3}\cos 8 + \frac{1}{3}$ $ \simeq 0.3818$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.