Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 8 - Complex Numbers, Polar Equations, and Parametric Equations - Section 8.6 Parametric Equations, Graphs, and Applications - 8.6 Exercises - Page 398: 13

Answer

(a) $x = 3~tan~t$ $y = 2~sec~t$ We can see the graph below. (b) $\frac{y^2}{4} - \frac{x^2}{9} = 1$

Work Step by Step

(a) $x = 3~tan~t$ $y = 2~sec~t$ When $t = -\frac{3\pi}{8}$: $x = 3~tan~\frac{-3\pi}{8} = -7.24$ $y = 2~sec~\frac{-3\pi}{8} = 5.23$ When $t = -\frac{\pi}{3}$: $x = 3~tan~\frac{-\pi}{3} = -5.20$ $y = 2~sec~\frac{-\pi}{3} = 4$ When $t = -\frac{\pi}{4}$: $x = 3~tan~\frac{-\pi}{4} = -3$ $y = 2~sec~\frac{-\pi}{4} = 2.83$ When $t = -\frac{\pi}{6}$: $x = 3~tan~\frac{-\pi}{6} = 1.73$ $y = 2~sec~\frac{-\pi}{6} = 2.31$ When $t = 0$: $x = 3~tan~0 = 0$ $y = 2~sec~0 = 2$ When $t = \frac{\pi}{6}$: $x = 3~tan~\frac{\pi}{6} = 1.73$ $y = 2~sec~\frac{\pi}{6} = 2.31$ When $t = \frac{\pi}{4}$: $x = 3~tan~\frac{\pi}{4} = 3$ $y = 2~sec~\frac{\pi}{4} = 2.83$ When $t = \frac{\pi}{3}$: $x = 3~tan~\frac{\pi}{3} = 5.20$ $y = 2~sec~\frac{\pi}{3} = 4$ When $t = \frac{3\pi}{8}$: $x = 3~tan~\frac{3\pi}{8} = 7.24$ $y = 2~sec~\frac{3\pi}{8} = 5.23$ We can see the graph below. (b) $x = 3~tan~t$ $tan~t = \frac{x}{3}$ $tan^2~t = \frac{x^2}{9}$ $y = 2~sec~t$ $sec~t = \frac{y}{2}$ $sec^2~t = \frac{y^2}{4}$ $sec^2~t - tan^2~t = 1$ $\frac{y^2}{4} - \frac{x^2}{9} = 1$
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