Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 5 - Section 5.5 - The Substitution Rule - 5.5 Exercises - Page 419: 79

Answer

$All$ $three$ $areas$ $are$ $equal.$

Work Step by Step

$Area$ $(1)$ $=$ $\int_{0}^{1}e^\sqrt{x}dx$ Let $u$ $=$ $\sqrt{x}$ Then $du$ $=$ $\frac{1}{2}$$x^\frac{-1}{2}$$dx$ $=$ $\frac{1}{2\sqrt x}$ $dx$ $=$ $\frac{1}{2u}$ $dx$ When $x$ $=$ $0$, then $u$ $=$ $0$ When $x$ $=$ $1$, then $u$ $=$ $1$ So, we have $Area$ $(1)$ $=$ $\int_{0}^{1}2{u}e^{u}du$ $Area$ $(2)$ $=$ $\int_{0}^{1}2{x}e^{x}dx$ [same as $Area$ $(1)$] $Area$ $(3)$ $=$ $\int_{0}^{1}e^\sqrt{sin(x)}sin(2x)dx$ $=$ $\int_{0}^{1}e^\sqrt{sin(x)}2sin(x)cos(x)dx$ Let $u$ $=$ $\sin(x)$ Then $du$ $=$ $\cos(x)dx$ When $x$ $=$ ${\pi/2}$, then $u$ $=$ $\sin(\pi/2)$ $=$ $1$ When $x$ $=$ $0$, then $u$ $=$ $\sin(0)$ $=$ $0$ So, we have $Area$ $(3)$ $=$ $\int_{0}^{1}2{u}e^{u}du$ [same as $Area$ $(1)$ and $Area$ $(2)$] $\Rightarrow$$All$ $three$ $areas$ $are$ $equal$
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