Demonstration of sum-over-paths or Path integral - powerful method of modern science. Understanding of "integral" concept is'nt needed.
Based on material from R. Feynman' book "QED - The Strange Theory Of Light And Matter", chapter 2, esp. pages 40 - 44. Points A, B, M1, M2, C on Graphics 1 and phases [math] \phi_1, \phi_2 [/math] on Graphics 2 are movable.