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
*Altitude (triangle)
*Angle bisector theorem
*Apollonius' theorem
*Barycentric coordinates (mathematics)
*Brianchon point
*Brocard circle
*Brocard points
*Brocard triangle
*Carnot's theorem
*Centroid
*Ceva's theorem
*Circumconic and inconic
*Circumscribed circle
*Cleaver (geometry)
*Congruence (geometry)
*Contact triangle
*Conway triangle notation
*CPCTC
*Delaunay triangulation
*de Longchamps point
*Desargues' theorem
*Encyclopedia of Triangle Centers
*Equal incircles theorem
*Equilateral triangle
*Euler's line
*Euler's theorem in geometry
*Fermat point
*Fuhrmann circle
*GEOS circle
*Gergonne point
*Heron's formula
*Hyperbolic triangle (non-Euclidean geometry)
*Hypotenuse
*Incircle and excircles of a triangle
*Inertia tensor of triangle
*Isosceles triangle
*Isodynamic point
*Isogonal conjugate
*Isotomic conjugate
*Isotomic lines
*Japanese theorem for concyclic polygons
*Johnson circles
*Kepler triangle
*Leg (geometry)
*Lester's theorem
*Mandart inellipse
*Medial triangle
*Median (geometry)
*Menelaus' theorem
*Mittenpunkt
*Morley's trisector theorem
*Nagel point
*Napoleon's theorem
*Nine-point circle
*Nine-point hyperbola
*One-seventh area triangle
*Orthocenter
*Orthocentric system
*Pedal triangle
*Pompeiu's theorem
*Pons asinorum
*Pythagorean theorem
*Right triangle
*Routh's theorem
*Scalene triangle
*Schwarz triangle
*Schiffler's theorem
*Sierpinski triangle (fractal geometry)
*Similarity (geometry)
*Simson line
*Special right triangles
*Spieker circle
*Spiral of Theodorus
*Splitter (geometry)
*Steiner inellipse
*Steiner-Lehmus theorem
*Stewart's theorem
*Symmedian
*Tarry point
*Ternary plot
*Thales' theorem
*Thomson cubic
*Triangle group
*Triangulation
*Triangular coordinates
*Trilinear coordinates
*Trisected perimeter point
*Wernau points

Inequalities

*Triangle inequality
*Barrow's inequality
*Erdős–Mordell inequality
*Euler's theorem in geometry
*Ono's inequality
*Pedoe's inequality
*Hadwiger-Finsler inequality
*Weitzenböck's inequality

Trigonometry

*Law of cosines
*Law of sines
*Law of tangents
*Rational trigonometry
*Spherical trigonometry
*Trigonometric function
*Trigonometry

Applied mathematics

* De Finetti diagram
* Triangle mesh
* Nonobtuse mesh

Resources

* Encyclopedia of Triangle Centers

Algebra

*Triangular factor
*Triangular matrix
*(2,3,7) triangle group

Number theory

*Boustrophedon transform
*Eulerian number
*Heronian triangle
*Lozanić's triangle
*Narayana number
*Pascal's triangle
*Pythagorean triple
*Rencontres numbers
*Stirling numbers of the first kind
*Stirling numbers of the second kind
*Triangular number

Geography

*Bermuda Triangle
*Sunni triangle
*Historic Triangle
*Parliamentary Triangle, Canberra
*Research Triangle

Anatomy

*Submandibular triangle
*Triangle choke
*Arm triangle choke
*Submental triangle
*Carotid triangle

Artifacts

*Triangle (instrument)
*Black triangle
*Triquetra