Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - 10.1 Curves Defined by Parametric Equations - 10.1 Exercises - Page 686: 21

Answer

$\left(\frac{x}{5}\right)^{2}+\left(\frac{y}{2}\right)^{2}=1$ from the point $(0,-2)$ clockwise around the ellipse $3$ times to the point $(0,-2)$.

Work Step by Step

$x$ = $5\sin t$ $\sin t$ = $\frac{x}{5}$ $y$ = $2\cos t$ $\cos t$ = $\frac{y}{2}$ Use the Pythagorean Identity: $\cos^2 z+\sin^2 z=1$ $\sin^{2}t+\cos^{2}t$ = $\left(\frac{x}{5}\right)^{2}+\left(\frac{y}{2}\right)^{2}$ = $1$ The motion of the particle takes place on an ellipse centered at $(0,0)$. As $t$ goes from $-\pi$ to $5\pi$, the particle starts at the point $(0,-2)$ and moves clockwise around the ellipse $3$ times because we have: $t=-\pi\Rightarrow (0,-2)$ $t=0\Rightarrow (0,2)$ $t=\pi\Rightarrow (0,-2)$ $t=2\pi\Rightarrow (0,2)$ $t=3\pi\Rightarrow (0,-2)$ $t=4\pi\Rightarrow (0,2)$ $t=5\pi\Rightarrow (0,-2)$
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