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: 40

Answer

\[\lim_{x\rightarrow 0}\frac{e^x-e^{-x}-2x}{x-\sin x}=2\]

Work Step by Step

Let \[l=\lim_{x\rightarrow 0}\frac{e^x-e^{-x}-2x}{x-\sin x}\] Which is $\frac{0}{0}$ form Using L'Hopital's rule \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{(e^x-e^{-x}-2x)'}{(x-\sin x)'}\] \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{e^x+e^{-x}-2}{1-\cos x}\] Which is again $\frac{0}{0}$ form Using L'Hopital's rule \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{(e^x+e^{-x}-2)'}{(1-\cos x)'}\] \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{e^x-e^{-x}}{\sin x}\] Which is again $\frac{0}{0}$ form Using L'Hopital's rule \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{(e^x-e^{-x})'}{(\sin x)'}\] \[\Rightarrow l=\lim_{x\rightarrow 0}\frac{e^x+e^{-x}}{\cos x}\] \[\Rightarrow l=\frac{2}{1}=2\] Hence , \[\lim_{x\rightarrow 0}\frac{e^x-e^{-x}-2x}{x-\sin x}=2\]
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