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: 22

Answer

(a) Center: $C(0,-5)$ $V_1(0,-10)$ and $V_2(0,0)$ $F_1(0,-5-\sqrt {22})$ and $F_2(0,-5+\sqrt {22})$ (b) Length of the major axis: $2a=10$ Length of the minor axis: $2b=2\sqrt 3$ (c)

Work Step by Step

Equation of an ellipse with center at $(h,k)$ (major axis is vertical): $\frac{(x-h)^2}{b^2}+\frac{(y-k)^2}{a^2}=1$ $\frac{x^2}{3}+\frac{(y+5)^2}{25}=1$ $\frac{(x-0)^2}{(\sqrt 3)^2}+\frac{[y-(-5)]^2}{5^2}=1$ $h=0$ $k=-5$ Center: $C(0,-5)$ $a=5$ $b=\sqrt 3$ $c^2=a^2-b^2=25-3=22$ $c=\sqrt {22}$ The given equation can be obtained by shifting $\frac{x^2}{(\sqrt 3)^2}+\frac{y^2}{5^2}=1$ downward 5 units. In this equation: Vertices: $V(0,±a)$ $V_1(0,-5)$ and $V_2(0,5)$ Foci: $F(0,±c)$ $F_1(0,-\sqrt {22})$ and $F_2(0,\sqrt {22})$ Now, shift these points 5 units downward: $V_1(0,-10)$ and $V_2(0,0)$ $F_1(0,-5-\sqrt {22})$ and $F_2(0,-5+\sqrt {22})$ Length of the major axis: $2a=10$ Length of the minor axis: $2b=2\sqrt 3$
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