The Math Forum had a contest to see who could come up with the most ways to construct an ellipse. Michael Thwaites won, with 13. 11 of them were done in Cabri Geometre:

- 2x1 Concentric Circles
- Ellipse by Focus and Directrix
- A False Ellipse
- From 5 Fixed Points and 1 Free
- From Length and Two Foci
- From a Sketchpad Sketch
- Intersecting Linkages
- Invert a Point
- Ladder Against a Wall
- Linear Distortion of a Circle
- Poles of Tangents of a Circle
- Tangents to a Circle Through a Point
- Taxi Cab Ellipse

The other two were done in Sketchpad: