High Quality Content by WIKIPEDIA articles! In geometry an arrangement of lines is the partition of the plane formed by a collection of lines. Bounds on the complexity of arrangements have been studied in discrete geometry, and computational geometers have found algorithms for the efficient construction of arrangements.For any set A of lines in the Euclidean plane, one can define an equivalence relation on the points of the plane according to which two points p and q are equivalent if, for every line l of A, either p and q are both on l or both belong to the same open half-plane bounded by l.