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A clique-sum of two planar graphs and the Wagner graph, forming a K 5-free graph. In graph theory , Wagner's theorem is a mathematical forbidden graph characterization of planar graphs , named after Klaus Wagner , stating that a finite graph is planar if and only if its minors include neither K 5 (the complete graph on five vertices ) nor K 3,3 ...
In November 2023, Desmos gave users the ability to bring sound to their graphs, allowing them to produce tones of a given frequency and gain. [14] Users can create accounts and save the graphs and plots that they have created to them. A permalink can then be generated which allows users to share their graphs and elect to be considered for staff ...
In all cases, including those in which the distribution is neither discrete nor continuous, the mean is the Lebesgue integral of the random variable with respect to its probability measure. The mean need not exist or be finite; for some probability distributions the mean is infinite (+∞ or −∞), while for others the mean is undefined.
An independent set of ⌊ ⌋ vertices (where ⌊ ⌋ is the floor function) in an n-vertex triangle-free graph is easy to find: either there is a vertex with at least ⌊ ⌋ neighbors (in which case those neighbors are an independent set) or all vertices have strictly less than ⌊ ⌋ neighbors (in which case any maximal independent set must have at least ⌊ ⌋ vertices). [4]
Named after Pierre-Simon Laplace, the graph Laplacian matrix can be viewed as a matrix form of the negative discrete Laplace operator on a graph approximating the negative continuous Laplacian obtained by the finite difference method. The Laplacian matrix relates to many useful properties of a graph.
Applying the Mycielskian repeatedly, starting with the one-edge graph, produces a sequence of graphs M i = μ(M i−1), sometimes called the Mycielski graphs. The first few graphs in this sequence are the graph M 2 = K 2 with two vertices connected by an edge, the cycle graph M 3 = C 5 , and the Grötzsch graph M 4 with 11 vertices and 20 edges.
The exponential graph K G is the graph with all functions V(G) → V(K) as vertices (not only homomorphisms) and two functions f,g adjacent when f(v) is adjacent to g(v') in K, for all adjacent vertices v,v ' of G. In particular, there is a loop at a function f (it is adjacent to itself) if and only if the function gives a homomorphism from G to K.
A subdivision of a graph is a graph formed by subdividing its edges into paths of one or more edges. Kuratowski's theorem states that a finite graph G {\displaystyle G} is planar if it is not possible to subdivide the edges of K 5 {\displaystyle K_{5}} or K 3 , 3 {\displaystyle K_{3,3}} , and then possibly add additional edges and vertices, to ...