List of triangle topics

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

Triangle Acute and obtuse triangles Altern base Altitude (triangle) Area bisector of a triangle Angle bisector of a triangle Angle bisector theorem Apollonius point Apollonius' theorem Automedian triangle Barrow's inequality Barycentric coordinates (mathematics) Brianchon point Brocard circle Brocard points Brocard triangle Carnot's theorem (conics) Carnot's theorem (inradius, circumradius) Centroid Ceva's theorem Cevian Circumconic and inconic Circumscribed circle Cleaver (geometry) Congruence (geometry) Congruent isoscelizers point Contact triangle Conway triangle notation CPCTC Delaunay triangulation de Longchamps point Desargues' theorem Droz-Farny line theorem Encyclopedia of Triangle Centers Equal incircles theorem Equal parallelians point Equidissection Equilateral triangle Euler's line Euler's theorem in geometry Erdős–Mordell inequality Exeter point Exterior angle theorem Fermat point Fermat's right triangle theorem Fuhrmann circle GEOS circle Gergonne point Golden triangle (mathematics) Gossard perspector	Hadley's theorem Hadwiger–Finsler inequality Heilbronn triangle problem Heptagonal triangle Heronian triangle Heron's formula Hofstadter points Hyperbolic triangle (non-Euclidean geometry) Hypotenuse Incircle and excircles of a triangle Inellipse Integer triangle Isodynamic point Isogonal conjugate Isoperimetric point Isosceles triangle Isosceles triangle theorem Isotomic conjugate Isotomic lines Jacobi point Japanese theorem for concyclic polygons Johnson circles Kepler triangle Kobon triangle problem Kosnita's theorem Leg (geometry) Lemoine's problem Lester's theorem List of triangle inequalities Mandart inellipse Medial triangle Median (geometry) Menelaus' theorem Miquel's theorem Mittenpunkt Monsky's theorem Morley centers Morley triangle Morley's trisector theorem Musselman's theorem Nagel point Napoleon points Napoleon's theorem Nine-point circle Nine-point hyperbola One-seventh area triangle Orthocenter Orthocentric system Orthocentroidal circle Orthopole	Pappus' area theorem Parry point Pedal triangle Perimeter bisector of a triangle Perpendicular bisectors of triangle sides Polar circle (geometry) Pompeiu's theorem Pons asinorum Pythagorean theorem Reuleaux triangle Regiomontanus Regiomontanus' angle maximization problem Right triangle Routh's theorem Scalene triangle Schwarz triangle Schiffler's theorem Sierpinski triangle (fractal geometry) Similarity (geometry) Similarity system of triangles Simson line Special right triangles Spieker center Spieker circle Spiral of Theodorus Splitter (geometry) Steiner circumellipse Steiner inellipse Steiner–Lehmus theorem Stewart's theorem Steiner point Symmedian Tangential triangle Tarry point Ternary plot Thales' theorem Thomson cubic Triangle center Triangle group Triangle inequality Triangular coordinates Triangular bipyramid Triangular prism Triangular pyramid Triangular tiling Triangulation Trilinear coordinates Trilinear polarity Trisected perimeter point Viviani's theorem Wernau points Yff center of congruence
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

Algebra

• Triangular matrix
• (2,3,7) triangle group

Number theory

Triangular arrays of numbers

Main article: Triangular array

• 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
• Parliamentary Triangle, Canberra
• Research Triangle
• Sunni Triangle
• Triangular trade

Anatomy

• Submandibular triangle
• Triangle choke
• Arm triangle choke
• Submental triangle
• Carotid triangle

Artifacts

• Black triangle
• Triangle (musical instrument)
• Triangular prism (optics)
• Triquetra

Symbols

• Eye of Providence
• Valknut