Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 4 - Section 4.4 - Indeterminate Forms and l''Hospital''s Rule - 4.4 Exercises - Page 316: 17

Answer

$\frac{1}{4}$

Work Step by Step

$$\eqalign{ & \mathop {\lim }\limits_{x \to 1} \frac{{\sin \left( {x - 1} \right)}}{{{x^3} + x - 2}} \cr & {\text{Use the quotient property of limits}} \cr & = \frac{{\mathop {\lim }\limits_{x \to 1} \left[ {\sin \left( {x - 1} \right)} \right]}}{{\mathop {\lim }\limits_{x \to 1} \left( {{x^3} + x - 2} \right)}} \cr & {\text{Evaluate the limit}} \cr & = \frac{{\sin \left( {1 - 1} \right)}}{{{{\left( 1 \right)}^3} + \left( 1 \right) - 2}}{\text{ = }}\frac{0}{0} \cr & {\text{The limit is an indeterminate form type }}\frac{0}{0},{\text{ so we can apply}} \cr & {\text{the L'Hospital's Rule}}{\text{.}} \cr & \mathop {\lim }\limits_{x \to 1} \frac{{\sin \left( {x - 1} \right)}}{{{x^3} + x - 2}} = \mathop {\lim }\limits_{x \to 1} \frac{{\frac{d}{{dx}}\left[ {\sin \left( {x - 1} \right)} \right]}}{{\frac{d}{{dx}}\left[ {{x^3} + x - 2} \right]}} \cr & = \mathop {\lim }\limits_{x \to 1} \frac{{\cos \left( {x - 1} \right)}}{{3{x^2} + 1}} \cr & {\text{Evaluate the limit when }}x \to 1 \cr & = \frac{{\cos \left( {1 - 1} \right)}}{{3{{\left( 1 \right)}^2} + 1}} \cr & = \frac{1}{4} \cr & {\text{Therefore}}{\text{,}} \cr & \mathop {\lim }\limits_{x \to 1} \frac{{\sin \left( {x - 1} \right)}}{{{x^3} + x - 2}} = \frac{1}{4} \cr} $$
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