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: 42

Answer

$1$

Work Step by Step

Our aim is to evaluate the limit for $\lim\limits_{x \to 0^{+}} (-\ln x)^x$ Let us consider that $y=\lim\limits_{x \to 0^{+}} (-\ln x)^x \implies \ln y=\lim\limits_{x \to 0^{+}} \dfrac{\ln [-\ln (x)]}{1/x}$ Apply L-Hospital's rule which can be defined as: $\lim\limits_{x \to a} \dfrac{P(x) }{Q(x)}=\lim\limits_{x \to a}\dfrac{P'(x)}{Q'(x)}$ where, $a$ can be any real number, infinity or negative infinity. $\lim\limits_{x \to 0^{+}} \ln y=\lim\limits_{x \to 0^{+}} ( \dfrac{1}{\ln x} ) (\dfrac{-1}{x})(-x^2) \\=\lim\limits_{x \to 0^{+}} \dfrac{x}{\ln x}\\=0$ Thus, we have: $\ln y=0 \implies y=e^0=1$
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