# Equation of an Ellipse

Like parabola, hyperbola and circle, an ellipse is also a conic section. Ellipse is a closed two-dimensional curve which is obtained when a cone is intersected by a plane that is not parallel to its base, as shown in the following figure:

Circle is a special case of ellipse. When the intersecting plane is parallel to the base of the cone, a circle is formed. We can think of an ellipse as a circle which is pressed at the top. An ellipse is a locus of a point, sum of whose distances from two fixed points inside the elliptic curve is a constant.

Astronomers, initially, had an impression that the orbits of planets are oval, but later **Kepler** discovered that orbits of each planet is an ellipse and sun is at one of its foci.