Mathematics
Grade 12
15 min
Find properties of ellipses
Find properties of ellipses
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1
Introduction & Learning Objectives
Learning Objectives
Identify the center, vertices, co-vertices, and foci of an ellipse from its standard equation.
Determine whether an ellipse has a horizontal or vertical major axis.
Calculate the lengths of the major and minor axes.
Compute the eccentricity of an ellipse and interpret its meaning.
Convert the general form of an ellipse's equation to its standard form by completing the square.
Sketch the graph of an ellipse using its key properties.
Ever wondered why planets travel in elliptical orbits and not perfect circles? 🪐 Let's uncover the mathematical properties that govern these cosmic paths!
This tutorial will guide you through the process of deconstructing the equation of an ellipse to find all its essential characteristics. Mastering these propertie...
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Key Concepts & Vocabulary
TermDefinitionExample
EllipseA set of all points (x, y) in a plane, the sum of whose distances from two distinct fixed points, called foci, is constant.If the foci are at (-3, 0) and (3, 0), and the constant sum is 10, a point like (5, 0) is on the ellipse because the distance to (-3, 0) is 8 and the distance to (3, 0) is 2, and 8 + 2 = 10.
Foci (singular: Focus)The two fixed points inside the ellipse that are used to define its shape. The distance from the center to each focus is denoted by 'c'.In the ellipse (x^2/25) + (y^2/9) = 1, the foci are located at (-4, 0) and (4, 0).
VerticesThe endpoints of the major axis. They are the two points on the ellipse that are farthest apart.For the ellipse (x^2/25) + (y^2/9) = 1, the vertices are at (-5, 0) and (5, 0).
Co-verticesThe endpoi...
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Core Formulas
Standard Equation of an Ellipse (Center at (h, k))
Horizontal Major Axis: \frac{(x-h)^2}{a^2} + \frac{(y-k)^2}{b^2} = 1, where a > b > 0.
Vertical Major Axis: \frac{(x-h)^2}{b^2} + \frac{(y-k)^2}{a^2} = 1, where a > b > 0.
This is the standard form for any ellipse. The center is (h, k). The larger denominator is always a^2. If a^2 is under the x-term, the major axis is horizontal. If a^2 is under the y-term, it's vertical.
Focal Distance Relationship
c^2 = a^2 - b^2
This formula relates the semi-major axis length (a), the semi-minor axis length (b), and the distance from the center to a focus (c). Use this to find the location of the foci once you know a and b.
Eccentricity Formula
e = \frac{c}{a}
This formula calculates the eccentricity 'e...
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Challenging
Consider Ellipse A with equation \frac{x^2}{100} + \frac{y^2}{99} = 1 and Ellipse B with equation \frac{x^2}{36} + \frac{y^2}{11} = 1. Which statement is true?
A.Ellipse A is more elongated than Ellipse B.
B.Ellipse B is more elongated than Ellipse A.
C.Both ellipses have the same eccentricity.
D.Both ellipses are perfect circles.
Challenging
An ellipse is defined as the set of all points (x, y) such that the sum of the distances from (x, y) to the foci F1(-4, 0) and F2(4, 0) is 10. What is the length of the minor axis of this ellipse?
A.5
B.10
C.6
D.3
Challenging
The vertices of an ellipse are at (1, 8) and (1, -4). If its eccentricity is e = 2/3, what is the length of the minor axis?
A.4\sqrt{5}
B.2\sqrt{5}
C.20
D.8
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