ELLIPSE

Formed when a plane intersects a cone at an angle to the base. The collection of all points such that the sum of the distances from a point, (x, y), on the ellipse to two fixed points, the foci, is constant. The line that passes through the two foci intersects the ellipse at two points, the vertices. The chord that joins these vertices is called the major axis. The midpoint of the major axis is the center of the ellipse. The center is also the midpoint of the minor axis, which is a chord perpendicular to the major axis.