Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 11: Parametric Equations and Polar Coordinates - Section 11.6 - Conic Sections - Exercises 11.6 - Page 678: 42

Answer

$ a.\qquad$ New center: $\quad (-3, -2)$ New foci: $\quad (-3,-6)$ and $(-3,2)$ New vertices: $\quad (-3,-7)$ and $(-3,3)$ $ b.\qquad$ See graph.

Work Step by Step

$ a.\qquad$ $\displaystyle \frac{x^{2}}{9}+\frac{y^{2}}{25}=1$ Which is of the form $\displaystyle \quad\frac{x^{2}}{b^{2}}+\frac{y^{2}}{a^{2}}=1 \quad (a\gt b)$ Foci on the x-axis, Center: $(0,0),\quad a=5,\quad b=3$ Center-to-focus distance: $\quad c=\sqrt{a^{2}-b^{2}}=\sqrt{25-9}=4$ Foci: $\quad(0,\pm c)= \quad(0,\pm 4)$ Vertices: $\quad (0,\pm a)= \quad (0,\pm 5)$ The translations are such that $(x,y)\rightarrow(x',y')$, where $\left\{\begin{array}{ll} x'=x-3 & \text{... shift left}\\ y'=y-2 & \text{... shift down} \end{array}\right.$ New center: $(-3+0,-2+0)=(-3,-2)$ New foci: $\quad(-3+0-2\pm c)= \quad(-3,-2\pm 4)$, $(-3,-6)$ and $(-3,2)$ New vertices: $\quad (-3+0,-2\pm a)= \quad (-3,-2\pm 5)$ $(-3,-7)$ and $(-3,3)$ $ b.\qquad$ See graph.
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