Thomas' Calculus 13th Edition

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

Chapter 7: Transcendental Functions - Practice Exercises - Page 440: 88

Answer

$$\frac{1}{2}$$

Work Step by Step

$$\eqalign{ & \mathop {\lim }\limits_{x \to 0} \frac{{\tan x}}{{x + \sin x}} \cr & {\text{Evaluating, we get:}} \cr & = \frac{{\tan 0}}{{0 + \sin 0}} \cr & = \frac{0}{0} \cr & {\text{Using l'Hopital's rule:}} \cr & = \frac{{\mathop {\lim }\limits_{x \to 0} \frac{d}{{dx}}\left( {\tan x} \right)}}{{\mathop {\lim }\limits_{x \to 0} \frac{d}{{dx}}\left( {x + \sin x} \right)}} \cr & = \mathop {\lim }\limits_{x \to 0} \frac{{{{\sec }^2}x}}{{1 + \cos x}} \cr & {\text{Evaluating the limit, we get:}} \cr & = \frac{{{{\sec }^2}0}}{{1 + \cos 0}} \cr & = \frac{1}{{1 + 1}} \cr & = \frac{1}{2} \cr & {\text{Then}} \cr & \mathop {\lim }\limits_{x \to 0} \frac{{\tan x}}{{x + \sin x}} = \frac{1}{2} \cr} $$
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