{{One source|date=July 2024}}{{Distinguish|Triangular graph|Ternary plot}} {{infobox graph | name = Triangle graph | image = 160px | image_caption = The triangle graph | vertices = ''3'' | edges = ''3'' | automorphisms = 6 (''D<sub>3</sub>'') | chromatic_number = 3 | chromatic_index = 3 | diameter = 1 | radius = 1 | girth = 3 | notation = <math>C_3</math> or <math>K_3</math> | properties = 2-regular<br>Vertex-transitive<br>Edge-transitive<br>Unit distance<br>Hamiltonian<br>Eulerian }}
In the mathematical field of graph theory, the '''triangle graph''' is a planar undirected graph with 3 vertices and 3 edges, in the form of a triangle.<ref>{{MathWorld|urlname=TriangleGraph|title=Triangle Graph}}</ref>
The triangle graph is also known as the cycle graph <math>C_3</math> and the complete graph <math>K_3</math>.
== Properties == The triangle graph has chromatic number 3, chromatic index 3, radius 1, diameter 1 and girth 3. It is also a 2-vertex-connected graph and a 2-edge-connected graph.
Its chromatic polynomial is <math>(x-2)(x-1)x.</math>
==See also== * Triangle-free graph
== References == {{reflist}}
Category:Individual graphs Category:Regular graphs