Calculus: Early Transcendentals (2nd Edition)

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

Chapter 9 - Power Series - 9.4 Working with Taylor Series - 9.4 Exercises - Page 702: 14

Answer

$1$

Work Step by Step

Our aim is to find the limit by using a Taylor's series. $L=\lim\limits_{x \to \infty} x \sin x \dfrac{1}{x}$ Recall the series for $\sin x=\Sigma_{k =0}^{\infty} (-1)^k \dfrac{(x)^{2k+1}}{(2k+1)!}$ Now, $L=\lim\limits_{t \to 0}\dfrac{1}{t} \sin t\\=\lim\limits_{t \to 0}\dfrac{1}{t} \Sigma_{k =0}^{\infty} (-1)^k \dfrac{(t)^{2k+1}}{(2k+1)!}\\=\lim\limits_{t \to 0}[(-1)^0 \dfrac{(t)^{(2)(0)}}{(2(0)+1)!}+(-1)^1 \dfrac{(t)^{(2)(1)}}{(2(1)+1)!}+(-1)^2 \dfrac{(t)^{(2)(2)}}{(2(2)+1)!}+.........)\\=1-\dfrac{0^2}{3!}+\dfrac{0^4}{5!}+..........\\=1$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.