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: 91

Answer

For the parametrization $(t^3,t^6)$, the area is $\frac{1}{3}$. For the parametrization $(t^2,t^4)$, the area is $\frac{1}{3}$.

Work Step by Step

1. Parametrization: $(t^3,t^6)$ So, we have $x\left( t \right) = {t^3}$, $x'\left( t \right) = 3{t^2}$. $y\left( t \right) = {t^6}$. Since $x\left( t \right)$ is increasing, the $x$-interval $\left[ {0,1} \right]$ corresponds to the $t$-interval $\left[ {0,1} \right]$. Using Eq. (11) the area is $A = \mathop \smallint \limits_{t = 0}^1 {t^6}\left( {3{t^2}} \right){\rm{d}}t = 3\mathop \smallint \limits_{t = 0}^1 {t^8}{\rm{d}}t = \frac{3}{9}{t^9}|_0^1 = \frac{1}{3}$. 2. Parametrization: $(t^2,t^4)$ So, we have $x\left( t \right) = {t^2}$, $x'\left( t \right) = 2t$. $y\left( t \right) = {t^4}$. Since $x\left( t \right)$ is increasing, the $x$-interval $\left[ {0,1} \right]$ corresponds to the $t$-interval $\left[ {0,1} \right]$. Using Eq. (11) the area is $A = \mathop \smallint \limits_{t = 0}^1 {t^4}\left( {2t} \right){\rm{d}}t = 2\mathop \smallint \limits_{t = 0}^1 {t^5}{\rm{d}}t = \frac{2}{6}{t^6}|_0^1 = \frac{1}{3}$.
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