Theorems in plane geometry

A Angle bisector theorem Apollonius' theorem B Bézout's theorem Blaschke–Lebesgue theorem British flag theorem C Carnot's theorem Ceva's theorem E Equal incircles theorem Exterior angle theorem F Five circles theorem G Geometric mean theorem

H Heron's formula I Isosceles triangle theorem L Law of cosines Law of sines Law of tangents Lester's theorem M Menelaus' theorem Morley's trisector theorem N Napoleon's theorem O Ortsbogen theorem P Parallelogram law

P cont. Pitot theorem Pivot theorem Pizza theorem Pompeiu's theorem Pythagorean theorem R Routh's theorem S Seven circles theorem Steiner–Lehmus theorem Stewart's theorem T Thales' theorem

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