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: 94

Answer

The area is 1.

Work Step by Step

We have $x\left( t \right) = {{\rm{e}}^t}$, $x'\left( t \right) = {{\rm{e}}^t}$, $y\left( t \right)=t$. Using Eq. (11) the area is $A = \mathop \smallint \limits_{t = 0}^1 t\left( {{{\rm{e}}^t}} \right){\rm{d}}t = \mathop \smallint \limits_{t = 0}^1 t{{\rm{e}}^t}{\rm{d}}t$. Note that the indefinite form of this integral has been evaluated in Example 2 of Section 8.1. So, using integration by parts, it follows that $A = \mathop \smallint \limits_{t = 0}^1 t\left( {{{\rm{e}}^t}} \right){\rm{d}}t = \mathop \smallint \limits_{t = 0}^1 t{{\rm{e}}^t}{\rm{d}}t = t{{\rm{e}}^t}|_0^1 - {{\rm{e}}^t}|_0^1 = {\rm{e}} - {\rm{e}} + 1$. $A = 1$.
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