Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 6 - Applications of Integration - Review Exercises - Page 508: 29

Answer

$ \pi (e-1)^2 \text{cubic units}$

Work Step by Step

Our aim is to compute the volume of the given curve when it is revolved around $y$-axis by using the shell method. Shell method for computing the volume of the curve: Let us consider two functions $f(x)$ and $g(x)$ (both are continuous functions) with $f(x) \geq g(x)$ on the interval $[m, n]$ and $R$ defines the region which revolves about the y-axis and is known as the region bounded by the curves $y=f(x)$ and $y=g(x)$ between the lines $x=m$ and $x=n$. Then, the volume of the solid can be expressed as: $Volume, V=\int_m^n 2 \pi x [f(x)-g(x)] \ dx$ Here, $2\pi x=\text{Shell Circumference}$ and $[f(x)-g(x)] =\text {Height of the shell}$ We are given that $y=e^{x^2}$ and $y=e^{2-x^2}$ on $[0,1]$ Thus, $V=\int_m^n 2 \pi x [f(x)-g(x)] \ dx=2 \pi \int_0^1 x(e^{2-x^2}-e^{x^2}) \ dx$ or, $=2 \pi \times [- \dfrac{e^{2-x^2}}{2}-\dfrac{e^{x^2}}{2}]_0^1$ or, $=2 \pi \times [- \dfrac{e^{2-(1)^2}}{2}-\dfrac{e^{(1)^2}}{2}]$ or, $= \pi(-e-e+e^2+1)$ or, $= \pi (e-1)^2 \text{cubic units}$
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