Theorem 5.28(Eulers formula) If G is a connected plane graph with n vertices, e edges and f regions, then n-e+f-2. Proof. Induction on e, the casee=0 being as in this case n=le=0 and f=1 n-e+f=1-0+1=2▪ Theorem 5.28(Euler’s formula) If G is a connected plane graph with n vertices, e edges and f regions, then n -e+f= 2. ▪ Proof. Induction on e, the case e = 0 being as in this case n = 1, e = 0 and f =1 ▪ n-e+f=1-0+1=2