Laman's theorem
From Egres Open
Theorem (Laman [1]). A graph G=(V,E) is minimally rigid in 2 dimensions if and only if [math]|E|=2|V|-3[/math] and [math]i_G(X) \leq 2|X|-3[/math] for every [math]X \subseteq V[/math] of size at least 2.
