Problem
COM-B2-M07-P001 Sum of Degrees
#1
★★☆☆☆ Level 2 of 5
A graph has \(m\) edges. Prove that the sum of all vertex degrees is \(2m\).
Each edge has two endpoints.
In the sum of degrees, each edge is counted exactly twice: once at each endpoint. Therefore the sum of degrees is \(2m\).
A basic formula, but it should become automatic.