In this figure, the conic has one focus fixed at the origin. You can do two things to affect its shape:

• Drag the directrix
• Change the eccentricity,

The conic is then determined by the focus-directrix equation . If is a point on the conic, then the distance from to the focus at the origin is times the distance from to the directrix. All three types of conics -- ellipses, parabolas, and hyperbolas -- can be defined this way.