Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 11 - Section 11.2 - Ellipses - 11.2 Exercises - Page 797: 25

Answer

(a) Vertices: $V(±1,0)$ Foci: $F(±\frac{\sqrt 3}{2},0)$ Eccentricity: $e=\frac{\sqrt 3}{2}$ (b) Length of the major axis: $2a=2$ Length of the minor axis: $2b=1$ (c)

Work Step by Step

$x^2+4y^2=1$ $\frac{x^2}{1}+\frac{y^2}{\frac{1}{4}}=1$ $\frac{x^2}{1^2}+\frac{y^2}{(\frac{1}{2})^2}=1$ The major axis is horizontal. Equation of an ellipse when major axis is horizontal (center at the origin): $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ So: $a=1$ $b=\frac{1}{2}$ $c^2=a^2-b^2=1-\frac{1}{4}=\frac{3}{4}$ $c=\frac{\sqrt 3}{2}$ (a) Vertices: $V(±a,0)=V(±1,0)$ Foci: $F(±c,0)=F(±\frac{\sqrt 3}{2},0)$ Eccentricity: $e=\frac{c}{a}=\frac{\frac{\sqrt 3}{2}}{1}=\frac{\sqrt 3}{2}$ (b) Length of the major axis: $2a=2$ Length of the minor axis: $2b=1$
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