Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 6 - Inverse Functions - 6.8 Indeterminate Forms and I'Hospital's Rule - 6.8 Exercises - Page 500: 58

Answer

$1$

Work Step by Step

$y=\tan(2x)^x$ $\ln y = x\cdot \ln(\tan(2x))$ $\lim_{x\rightarrow 0^+} \ln y = \lim_{x\rightarrow 0^+} (x\cdot \ln(\tan(2x)))$ $=\lim_{x\rightarrow 0^+}\frac{\ln(\tan (2x))}{\frac{1}{x}}$ $=\lim_{x\rightarrow 0^+}\frac{\frac{1}{\tan(2x)}\cdot 2\sec^2(2x)}{-\frac{1}{x^2}}$ $=\lim_{x\rightarrow 0^+}\frac{-2\sec^2 (2x)\cdot x^2}{\tan(2x)}$ $=\lim_{x\rightarrow 0^+}\frac{-2x^2}{\sin(2x)\cos(2x)}$ $=\lim_{x\rightarrow 0^+}\frac{-x}{\cos(2x)}$ $=0$. $\lim_{x\rightarrow 0^+}y=e^0=1.$
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