Category:Complete Quadrilaterals

This category contains results about Complete Quadrilaterals.
Definitions specific to this category can be found in Definitions/Complete Quadrilaterals.

A complete quadrilateral is a quadrilateral whose $4$ lines are extended so as to form $6$ points of intersection.

These $6$ points are joined by a further $3$ diagonals.

In the above diagram, $AB$, $BC$, $CD$ and $DA$ are the initial $4$ straight lines forming the quadrilateral, whose further intersections are $S$ and $T$.

The point $R$ is the intersection of the two diagonals $AC$ and $BD$.

The third diagonal is $ST$.