Definition:Conic Section

Definition

 * [[File:ConicSections.gif]]

Take a double napped right circular cone $C$ whose base is $B$.

Let a plane $D$ intersect $C$.

Let $K$ be the set of points which forms the intersection of $C$ with $D$.

The nature of $K$ depends on the angle that $D$ makes with the base of $C$.

Circle
When $D$ and $B$ are parallel, then $K$ is a circle.