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: 39

Answer

$1$

Work Step by Step

Our aim is to evaluate the limit for $\lim\limits_{x \to 0^{+}} [-\dfrac{1}{\ln (x)}]^x$ Let us consider that $y=[-\dfrac{1}{\ln (x)}]^x \implies \ln y=x \ln (-\dfrac{1}{\ln x})$ Apply L-Hospital's rule to obtain: $\lim\limits_{x \to 0^{+}} \ln y=\lim\limits_{x \to 0^{+}} x \ln (-\dfrac{1}{\ln x})\\=\lim\limits_{x \to 0^{+}} -\dfrac{-(1/x\ln x)}{-1/x^2}\\=\lim\limits_{x \to 0^{+}} \dfrac{1/\ln x}{1/x}\\=0$ Thus, we have: $\lim\limits_{x \to 0^{+}} y=e^0=1$
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