Exterior Angle Theorem: Theorem, Elementary Geometry,

Apollonius' Theorem: Geometry, Theorem, Median (geometry), Triangle

Barrow's Inequality: Geometry, Triangle, Angle Bisector, Euler's Theorem in Geometry

Intersection Theorem: Projective Geometry, Incidence Structure, Theorem

Szemerédi's Theorem: Szemerédi Trotter Theorem, Mathematics, Combinatorial Geometry, Incidence (Geometry)