Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 5: Integrals - Section 5.6 - Definite Integral Substitutions and the Area Between Curves - Exercises 5.6 - Page 304: 47

Answer

$8$

Work Step by Step

The area between two graphs over [a,b], where one graph is above the other, is given with $\displaystyle \int_{a}^{b}(y_{above}-y_{below})dx$. --- Graphing, due to symmetry, the total area is 2$\times$(area right of the y-axis). For $x\in[0,1],\ \ y_{above}=x^{4}-4x^{2}+4,\ \ y_{below}=x^{2}$ $A_{1}=\displaystyle \int_{0}^{1}(x^{4}-5x^{2}+4)dx=\left[\frac{x^{5}}{5}-\frac{5x^{3}}{3}+4x \right]_{0}^{1}=\frac{1}{5}-\frac{5}{3}+4=\frac{38}{15}$ For $x\in[1,2],\ \ y_{above}=x^{2},\ \ y_{below}=x^{4}-4x^{2}+4$ $A_{2}=-\displaystyle \int_{1}^{2}(x^{4}-5x^{2}+4)dx=\\\\\displaystyle -\left[\frac{x^{5}}{5}-\frac{5x^{3}}{3}+4x \right]_{1}^{2}=-[ \frac{32-1}{5}-\frac{5(8-1)}{3}+4(2-1) ]=\frac{22}{15}$ Total area = $2(A_{1}+A_{2})=2(\displaystyle \frac{38}{15}+\frac{22}{15})=8$
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