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The Ellipse. Definition. Ellipse – is the set of all points in a plane such that the sum of the distances from two fixed points is constant. The two fixed points are called the foci of the ellipse. Graph of an Ellipse. Deriving the Formula. Note Write with distance formula Simplify.
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Definition Ellipse – is the set of all points in a plane such that the sum of the distances from two fixed points is constant. The two fixed points are called the foci of the ellipse.
Deriving the Formula Note Write withdistance formula Simplify
Major Axis on y-Axis • Standard form of equation becomes • In both cases • Length of major axis = 2a • Length of minor axis = 2b
What if the ellipse is not centered at the origin? • If it is centered at any point, (h,k), the ellipse is translated. It is moved right “h” units and up “k” units from the origin. • Consider: • The center is at (2,-3); the distance from the center to the right & left endpoint = 2; the distance to the top & bottom endpoint = 1 • Since a>b, the horizontal axis will be the major axis and the focal points will be on that axis of the ellipse.
Find Vertices, Foci Given the following equations, find the vertices and foci of these ellipses centered at (h, k):
What is the equation of an ellipse, centered at the origin with a horizontal axis=10 and vertical axis=8?
Find the Equation 1. Consider an ellipse with • Center at (0,3) • Minor axis of length 4 • Foci at (0,0) and (0,6) • What is the equation? 2. Find the coordinates of the center and foci and the lengths of the major and minor axes of the ellipse with equation
Eccentricity not so round very round A measure of the "roundness" of an ellipse
Eccentricity • Given measurements of an ellipse • c = distance from center to focus • a = ½ thelength of the major axis • Eccentricity
Eccentricity • What limitations can we place on c in relationship to a? • c < a • What limitationsdoes this put on • When e is close to 0, graph is almost a circle • When e close to 1, the graph is long and thin
Finding the Eccentricity • Given an ellipse with • Center at (2,-2) • Vertex at (7,-2) • Focus at (4,-2) • What is the eccentricity? • Remember that
Whispering Gallery The Whispering Gallery is constructed in the form of an ellipsoid, with a parabolic dish at each focus. When a visitor stands at one dish and whispers, the line of sound emanating from this focus reflects directly to the dish/focus at the other end of the room, and to the other person! At Chicago Museumof Science andIndustry
Elliptical Orbits Planets travel in elliptical orbits around the sun.
Elliptical Orbits MeanDist • Perihelion • Distance from focus to closest approach • Aphelion • Distance from focus to farthest reach • Mean Distance • Half the majoraxis