Calculus (3rd Edition)

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

Chapter 8 - Techniques of Integration - 8.9 Numerical Integration - Exercises - Page 457: 26


$V\approx 1.98595$

Work Step by Step

Given $$y=e^{ -x^2} ; \quad\left[0,1\right] ; \quad y \text { -axis; } \quad T_{8}$$ Since $ V= 2\pi \int_{0}^{1} xe^{ -x^2}dx$ Now, we will evaluate the integral using $T_8$, since $\Delta x=\dfrac{b-a}{n}=\dfrac{1}{8}$ $T_{n}=\dfrac{1}{3}[y_0+4y_1+2y_2+..+4y_{N-3}+2y_{N-2}+4y_{N-1}+y_N]\Delta x\\ T_{8}=\dfrac{1}{3}[y_0+4y_1+2y_2+..+4y_{N-3}+2y_{N-2}+y_N]\Delta x$ The volume can be approximated as: $V= 2\pi \int_{0}^{1} xe^{ -x^2}dx \approx 2 \pi S_8 \\ \approx 2\pi (\dfrac{1}{3}) \dfrac{1}{8} [0+4(\dfrac{1}{8}e^{-1/64}++4(\dfrac{7}{8}e^{-49/64}+e^{-1}]\\ \approx 1.98595$ Hence, $V\approx 1.98595$
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