Brianchon theorem

If an hexagon $ABCDEF$ (not necessarily convex) is inscribed into a conic (in particular into a circle), then the three diagonals $AD,BE,CF$ are concurrent. This theorem is the dual of Pascal line theorem. (C. Brianchon, 1806)

Proof:It follows by duality.

Title	Brianchon theorem
Canonical name	BrianchonTheorem
Date of creation	2013-03-22 14:04:29
Last modified on	2013-03-22 14:04:29
Owner	vmoraru (1243)
Last modified by	vmoraru (1243)
Numerical id	7
Author	vmoraru (1243)
Entry type	Theorem
Classification	msc 51-00