Theorem
A graph is planar if and only if it has a drawing in which all pairs of vertex-disjoint edges cross an even number of times.
Click on the image.
The theorem is named after Haim Hanani (1934) and Bill Tutte (1970) who rediscovered it and invented the algebraic setting.
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου