Ellipses (Jump to: Lecture | Video )

An ellipse is a set of all points on a plane where the sum of the distances from any two fixed points is constant. These points are called the foci.

Figure 1.

Above, we have an ellipse with its vertex at (0, 0).

An ellipse has a major axis and a minor axis, which intersect in the center.

Figure 2.

Equation of an Ellipse
The equation for an ellipse depends on if it is horizontal or vertical (as determined by its major axis).

Figure 3.

Above, an ellipse is graphed next to its equation.