I am given an assignment to prove the hand shaking theorem, I don't know how to prove it.
closed as not a real question by Gerry Myerson, Ross Millikan, t.b., Jonas Meyer, Sivaram Jun 5 '11 at 1:27
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i have done this consider the following undirected graph
I see that ; deg(A)=2, deg(B)=2 , deg(C)=2, deg(D)=2 number of edges, e=4 then, 2e=8
so, 2e=summation of degree of all vertices on the graph