Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 12 - Parametric Equations, Polar Coordinates, and Conic Sections - 12.1 Parametric Equations - Exercises - Page 605: 96

Answer

The area is $A = 2\ln 2 - 1$.

Work Step by Step

At $t=1$, $c\left( 1 \right) = \left( {0,1} \right)$; whereas at $t=2$, $c\left( 2 \right) = \left( {\ln 2,0} \right)$. Plotting several points in $t$-interval $1 \le t \le 2$ and connecting them, we obtain the graph. We have $x\left( t \right) = \ln t$, $x'\left( t \right) = \frac{1}{t}$, $y\left( t \right) = 2 - t$. Using Eq. (11) the area is $A = \mathop \smallint \limits_{t = 1}^2 \left( {2 - t} \right)\frac{1}{t}{\rm{d}}t = \mathop \smallint \limits_{t = 1}^2 \left( {\frac{2}{t} - 1} \right){\rm{d}}t$. Since $\mathop \smallint \limits_{}^{} \frac{1}{t}{\rm{d}}t = \ln t$, we get $A = 2\mathop \smallint \limits_{t = 1}^2 \frac{1}{t}{\rm{d}}t - \mathop \smallint \limits_{t = 1}^2 {\rm{d}}t = 2\ln t|_1^2 - t|_1^2 = 2\ln 2 - 1$.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.