David Van Leeuwen's animation 4 or 5? David Van Leeuwen's animation by GeoGebra is a good explanation. http://www.geogebratube.org/student/m107691 Yutaka Nishiyama Reply
4 or 5? David Van Leeuwen's animation by GeoGebra is a good explanation.
http://www.geogebratube.org/student/m107691
Yutaka Nishiyama