# Ellipse

A plane through a right angle cone. The circle is a special case of the ellipse, an ellipse with an eccentricity of zero.

- The equation of an ellipse is given by

- where

- This may be approximated as

### Eccentricity

The eccentricity e of an ellipse can be computed by the formula:

where: a is the semimajor axis and b is the semiminor axis.

### Linear Eccentricity

The ratio of the distance between the center and focus of an ellipse to its semimajor axis.

**See also: **Circle, Conic Section, Eccentricity, Ellipsoid, Focal Radius, Latus Rectum, Oblate Spheroid.

**Subjects: ** Mathematics