Category:Ellipses

This category contains results about Ellipses.
Definitions specific to this category can be found in Definitions/Ellipses.

Let $D$ be a straight line.

Let $F$ be a point.

Let $e \in \R: 0 < e < 1$.

Let $K$ be the locus of points $P$ such that the distance $p$ from $P$ to $D$ and the distance $q$ from $P$ to $F$ are related by the condition:

$e p = q$

Then $K$ is an ellipse.