Calculus 10th Edition

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

Chapter 7 - Applications of Integration - 7.2 Exercises - Page 453: 6

Answer

$\text{Volume = $ \pi \left(48\sqrt 2 - \frac{272\sqrt 2}{15}\right) \approx 132.69$}$

Work Step by Step

$\text{It is given that}$ \begin{align} y = 4 - \frac{x^2}{4}; \ y = 2 \end{align} $\text{The intersections of these functions are}$ \begin{align} 4 - \frac{x^2}{4} = 2 \Rrightarrow x = \pm 2\sqrt 2 \end{align} $\text{Thus, the volume of the solid is}$ \begin{align} & V = \pi \int_{-2\sqrt 2}^{2\sqrt 2} \left( \left(4 - \frac{x^2}{4}\right)^2 -4\right) \ dx = \\ &= \pi \int_{-2\sqrt 2}^{2\sqrt 2} \left(12-2x^2+\frac{x^4}{16} \right) \ dx =c \left[12x - \frac{2x^3}{3} + \frac{x^5}{80} \right]_{-2\sqrt 2}^{2\sqrt 2} = \\ & = \pi \left(48\sqrt 2 - \frac{64\sqrt 2}{3} + - \frac{16\sqrt 2}{5}\right) = \pi \left(48\sqrt 2 - \frac{272\sqrt 2}{15}\right) \approx 132.69 \end{align}
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