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: 20

Answer

$$\frac{{dy}}{{dt}} = - \frac{{\ln t}}{{{t^2}}}$$

Work Step by Step

$$\eqalign{ & y = \frac{{1 + \ln t}}{t} \cr & {\text{Find the derivative of }}y{\text{ with respect to }}t \cr & \frac{{dy}}{{dt}} = \frac{d}{{dt}}\left[ {\frac{{1 + \ln t}}{t}} \right] \cr & {\text{use the quotient rule}} \cr & \frac{{dy}}{{dt}} = \frac{{t\frac{d}{{dt}}\left[ {1 + \ln t} \right] - \left( {1 + \ln t} \right)\frac{d}{{dt}}\left[ t \right]}}{{{t^2}}} \cr & {\text{solve the derivatives}} \cr & \frac{{dy}}{{dt}} = \frac{{t\left( {0 + \frac{1}{t}} \right) - \left( {1 + \ln t} \right)\left( 1 \right)}}{{{t^2}}} \cr & {\text{simplify}} \cr & \frac{{dy}}{{dt}} = \frac{{1 - 1 - \ln t}}{{{t^2}}} \cr & \frac{{dy}}{{dt}} = - \frac{{\ln t}}{{{t^2}}} \cr} $$
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