Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 6 - Exponential, Logarithmic, And Inverse Trigonometric Functions - 6.5 L'Hopital's Rule; Indeterminate Forms - Exercises Set 6.5 - Page 448: 49

Answer

$e^3$

Work Step by Step

Our aim is to evaluate the limit for $\lim\limits_{x \to 0^{+}} (\sin x)^{3/\ln x}$ Let us consider that $y=\lim\limits_{x \to 0^{+}} (\sin x)^{3/\ln x} \implies \ln y=\lim\limits_{x \to 0^{+}}\dfrac{3}{\ln x} \times \ln (\sin x)$ Apply L-Hospital's rule which can be defined as: $\lim\limits_{x \to a} \dfrac{P(x) }{Q(x)}=\lim\limits_{x \to a}\dfrac{P'(x)}{Q'(x)}$ $ \ln y=\lim\limits_{x \to 0^{+}}\dfrac{3 x \cos x}{\sin x}\\=3 \lim\limits_{x \to 0^{+}} (\cos x) \times \lim\limits_{x \to 0^{+}} \dfrac{x}{\sin x}\\=(3)(1)(1) \\=3$ Thus, we have: $\ln y=3\implies y=e^3$
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