This list of triangle topics includes things related to the geometric shape, either abstractly, as in idealizations studied by geometers, or in triangular arrays such as Pascal's triangle or triangular matrices, or concretely in physical space. It does not include metaphors like love triangle in which the word has no reference to the geometric shape.
Geometry
Trigonometry Differentiation of trigonometric functions Exact trigonometric constants History of trigonometry Inverse trigonometric functions Law of cosines Law of cotangents Law of sines Law of tangents List of integrals of inverse trigonometric functions List of integrals of trigonometric functions List of trigonometric identities Mollweide's formula Outline of trigonometry Rational trigonometry Sine Solution of triangles Spherical trigonometry Trigonometric functions Trigonometric substitution Trigonometric tables Trigonometry Uses of trigonometry
Applied mathematics De Finetti diagram Triangle mesh Nonobtuse mesh
Resources Encyclopedia of Triangle Centers Pythagorean Triangles The Secrets of Triangles
Algebra Triangular matrix (2,3,7) triangle group
Number theory
Triangular arrays of numbers
Bell numbers Boustrophedon transform Eulerian number Floyd's triangle Lozanić's triangle Narayana number Pascal's triangle Rencontres numbers Romberg's method Stirling numbers of the first kind Stirling numbers of the second kind Triangular number Triangular pyramidal number The (incomplete) Bell polynomials from a triangular array of polynomials (see also Polynomial sequence).
Integers in triangle geometry Heronian triangle Integer triangle Pythagorean triple Eisenstein triple
Geography Bermuda Triangle Historic Triangle Lithium Triangle Parliamentary Triangle, Canberra Research Triangle Sunni Triangle Triangular trade Rhubarb Triangle
Anatomy Submandibular triangle Triangle choke Arm triangle choke Submental triangle Carotid triangle Clavipectoral triangle Inguinal triangle Codman triangle
Artifacts Black triangle Triangle (musical instrument) Triangular prism (optics) Triquetra
Symbols Eye of Providence Valknut Shield of the Trinity