University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 9 - Section 9.1 - Sequences - Exercises - Page 490: 142

Answer

$ a.\quad$ Converges to $L=1.$. See image. Steps given below. $ b.\quad$ $N=5$ $N=41$

Work Step by Step

$a.\quad $ The steps you take will depend on the CAS you are using, but they follow the same logic. Using the free online CAS at "geogebra.org/cas": Cell 1: Enter the function representing the sequence $a(x)=x\displaystyle \sin(\frac{1}{x})$ From the dropdown menu, select "Table of values". In the dialog box for the table, set the range from 1 to 25, step 1. When we observe the graph, the points approach the line y=1. The sequence seems to converge to 1. In the next free cell of the CAS, we find the limit when $ n\rightarrow\infty$ Here, we enter "L=Limit(a, infinity)" (without quotes). The CAS returns the limit to be $L=1$. $ b.\quad$ $\epsilon=0.01.$ Define a function $g(x)=|L-a(x)|$ We want to find an integer after which $ g(x)\lt 0.01.$ Looking at the table of values we find that $a(5)$ is within $0.01$ of L. We take $N=5.$ $\epsilon=0.0001.$ Define a function $g(x)=|L-a(x)|$ We want to find an integer after which $ g(x)\lt 0.0001.$ Looking at the table of values (for n ranging from 1 to 25), there are none. We delete the table and create a new one, ranging from 26 to 50, step 1. We find that $a(41)$ is within $0.0001$ of L. We take $N=41.$
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