brianchons theorem

Input interpretation

Brianchon's theorem

Definition

The dual of Pascal's theorem. It states that, given a hexagon circumscribed on a conic section, the lines joining opposite polygon vertices (polygon diagonals) meet in a single point.
In 1847, Möbius gave a statement which generalizes Brianchon's theorem: if all lines (except possibly one) connecting two opposite vertices of a (4n + 2)-gon circumscribed on a conic section meet in one point, then the same is true for the remaining line.