Pappus' Theorem: Inscribe a hexagon (any six lines in a plane, with no three meeting at the same point) in an angle. Each pair of opposite sides are extended to intersection points. These interesection points (XYZ) form a straight line mapping their corresponding hexagonal points.
[url]http://mste.illinois.edu/dildine/classes/ci499fall04/pappus.html[/url]
