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

CPCTC: Geometry, Theorem, Congruence (geometry), Triangle

Defect (geometry): Geometry, Hyperbolic Triangle, Spherical Gauss Bonnet Theorem

Morley's Trisector Theorem: Plane Geometry, Triangle, Equilateral Triangle

Exterior Angle Theorem: Theorem, Elementary Geometry,