CabriJava demonstration of Brianchon's Theorem

Brianchon's Theorem states that, if alternate sides of a hexagon (AB'CA'BC' in the figure) are concurrent,
Then the lines joining opposite vertices are concurrent.
It is the dual of Pappus's Theorem.

You may move any of the points A,B,C,A',B',C'
by clicking on it and dragging it to a new position.
You will see that AA', BB' and CC' remain concurrent.

Main Cabri Page Cabri Java Official CabriJava Page