http://www.geogebra.org/en/upload/files/english/tierney-fife/Engine4Stroke_Exported.html
Designed by Pam Buffington and Peter Tierney-Fife of EDC in ME (USA). This is a temporary page and may be removed at any time.
Peter Tierney-Fife, Created with GeoGebra

amazing what humans can do with tools