A geometrical figure that is similar to a flattened circle. An ellipse can be obtained by cutting a right cone with a plane that is slightly tilted away from the position parallel to the base of the cone, but before it becomes parallel to one element of the cone.

A curve joining all points in a plane such that the sum of the distances to two fixed points (called foci) is always kept a constant. An ellipse looks like a flattened circle.

The equation of an ellipse with center at the origin is represented by x2/a2 + y2/b2 = 1, in which a is the length of the semimajor axis (half of the major axis), and b is the length of the semiminor axis (half of the minor axis). A major axis is the longest distance across an ellipse, and a minor axis is the shortest distance across an ellipse.

Related Terms: circle, hyperbola, parabola

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