Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 11 - Review - Exercises - Page 833: 21

Answer

(a) Center: $C(2,-3)$ $V_1(2,-9)$ and $V_2(2,3)$ $F_1(2,-3-3\sqrt 3)$ and $F_2(2,-3+3\sqrt 3)$ (b) Length of the major axis: $2a=12$ Length of the minor axis: $2b=6$ (c)

Work Step by Step

Equation of an ellipse with center at $(h,k)$ (major axis is vertical): $\frac{(x-h)^2}{b^2}+\frac{(y-k)^2}{a^2}=1$ $\frac{(x-2)^2}{9}+\frac{(y+3)^2}{36}=1$ $\frac{(x-2)^2}{3^2}+\frac{[y-(-3)]^2}{6^2}=1$ $h=2$ $k=-3$ Center: $C(2,-3)$ $a=6$ $b=3$ $c^2=a^2-b^2=36-9=27$ $c=3\sqrt 3$ The given equation can be obtained by shifting $\frac{x^2}{3^2}+\frac{y^2}{6^2}=1$ right 2 units and downward 3 units. In this equation: Vertices: $V(0,±a)$ $V_1(0,-6)$ and $V_2(0,6)$ Foci: $F(0,±c)$ $F_1(0,-3\sqrt 3)$ and $F_2(0,3\sqrt 3)$ Now, shift these points 2 units to the right and 3 units downward: $V_1(2,-9)$ and $V_2(2,3)$ $F_1(2,-3-3\sqrt 3)$ and $F_2(2,-3+3\sqrt 3)$ Length of the major axis: $2a=12$ Length of the minor axis: $2b=6$
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