Thomas' Calculus 13th Edition

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

Chapter 7: Transcendental Functions - Section 7.2 - Natural Logarithms - Exercises 7.2 - Page 381: 29

Answer

$$\frac{{dy}}{{dt}} = \frac{2}{{t{{\left( {1 - \ln t} \right)}^2}}}$$

Work Step by Step

$$\eqalign{ & y = \frac{{1 + \ln t}}{{1 - \ln t}} \cr & {\text{Find the derivative of }}y{\text{ with respect to }}t \cr & \frac{{dy}}{{dt}} = \frac{d}{{dt}}\left[ {\frac{{1 + \ln t}}{{1 - \ln t}}} \right] \cr & {\text{use the quotient rule}} \cr & \frac{{dy}}{{dt}} = \frac{{\left( {1 - \ln t} \right)\left( {1 + \ln t} \right)' - \left( {1 + \ln t} \right)\left( {1 - \ln t} \right)'}}{{{{\left( {1 - \ln t} \right)}^2}}} \cr & {\text{solve the derivatives and simplify}} \cr & \frac{{dy}}{{dt}} = \frac{{\left( {1 - \ln t} \right)\left( {\frac{1}{t}} \right) - \left( {1 + \ln t} \right)\left( { - \frac{1}{t}} \right)}}{{{{\left( {1 - \ln t} \right)}^2}}} \cr & \frac{{dy}}{{dt}} = \frac{{\frac{{1 - \ln t}}{t} + \frac{{1 + \ln t}}{t}}}{{{{\left( {1 - \ln t} \right)}^2}}} \cr & \frac{{dy}}{{dt}} = \frac{{1 - \ln t + 1 + \ln t}}{{t{{\left( {1 - \ln t} \right)}^2}}} \cr & \frac{{dy}}{{dt}} = \frac{2}{{t{{\left( {1 - \ln t} \right)}^2}}} \cr} $$
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