Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 6 - Inverse Functions - 6.8 Indeterminate Forms and I'Hospital's Rule - 6.8 Exercises - Page 500: 52

Answer

\[\lim_{x\rightarrow 0}(\csc x-\cot x)=0\]

Work Step by Step

Let \[l=\lim_{x\rightarrow 0}(\csc x-\cot x)\] Which is $\infty-\infty$ form \[l=\lim_{x\rightarrow 0}\left(\frac{1}{\sin x}-\frac{\cos x}{\sin x}\right)\] \[l=\lim_{x\rightarrow 0}\left(\frac{1-\cos x}{\sin x}\right)\] Which is $\frac{0}{0}$ form Using L' Hopital's rule \[l=\lim_{x\rightarrow 0}\frac{(1-\cos x)'}{(\sin x)'}\] \[l=\lim_{x\rightarrow 0}\frac{\sin x}{\cos x}\] \[\Rightarrow l=\frac{0}{1}=0\] Hence, \[\lim_{x\rightarrow 0}(\csc x-\cot x)=0\]
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