Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 2: Limits and Continuity - Section 2.6 - Limits Involving Infinity; Asymptotes of Graphs - Exercises 2.6 - Page 98: 52

Answer

The limit does not exist.

Work Step by Step

Applying the limit laws for a sum and a constant, if the limit L exists, then $L= 2-\displaystyle \lim_{\theta\rightarrow 0}\cot\theta$ You can sketch a unit circle. 0 radians is at (1,0)$;$ the positive direction is counterclockwise; the negative direction is clockwise. When $\theta\rightarrow 0^{-}$, it approaches 0 through the 4th quadrant, where $\cot\theta$ is negative, and $\displaystyle \lim_{\theta\rightarrow 0^{-}}\cot\theta=-\infty$ When $\theta\rightarrow 0^{+}$, it approaches 0 through the 1st quadrant, where $\cot\theta$ is positive, and $\displaystyle \lim_{\theta\rightarrow 0^{+}}\cot\theta=+\infty$ Since the one-sided limits differ, we say that the limit does not exist.
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