
theorem
  for F,G being Function st F,G are_fiberwise_equipotent for x1,x2 being
  set st x1 in dom F & x2 in dom F & x1 <> x2 holds ex z1,z2 being set st z1 in
  dom G & z2 in dom G & z1 <> z2 & F.x1 = G.z1 & F.x2 = G.z2 by Lm6;
