Archimedes Trammel

Drag B to observe how the trammel traces an ellipse.
Drag F to see how the same ellipse can be constructed with 2 pins and a piece of string.

This document requires an HTML5-compliant browser.

Altering |AB| and |AC| changes the ellipse.
Can you find a relationship between |AB|, AC| and |DE|, the distance between the foci?

App generated by Geometry Expressions