Ptolemaic graph
In graph theory , a Ptolemaic graph is an undirected graph whose shortest path distances obey Ptolemy's inequality , which in turn was named after the Greek astronomer and mathematician Ptolemy . 
<triplet> graph theory <subj> undirected graph <obj> studies <triplet> Ptolemaic graph <subj> Ptolemy <obj> named after <triplet> undirected graph <subj> graph theory <obj> studied by <triplet> Ptolemy's inequality <subj> Ptolemy <obj> named after <triplet> mathematician <subj> graph theory <obj> has part <triplet> Ptolemy <subj> mathematician <obj> field of work