All Projective Geometry

This group gathers theorems from projective geometry, the study of incidence, collinearity, and cross-ratio properties of points and lines that remain true under projection and do not depend on distance or parallelism. It covers the foundational incidence theorems of Desargues and Pappus, Pascal's theorem on hexagons inscribed in a conic and its dual, Brianchon's theorem, and Poncelet's closure theorem describing when a polygon inscribed in one conic and circumscribed about another must close up after a fixed number of steps regardless of the starting point.