Van Schooten's Locus Problem

 

Construct an animation showing the inscribed ellipse of an astroid.

Construct an animation showing the tangent sweeping out the interior of the astroid.

Two verttices of a rigid triangle slide along two perpendicular lines; what does the third vertex describe?

Show that it is possible for a  triangle move rigidly with vertices traveling along three ellipses of different sizes and axes.

See also