reserve E,V for set, G,G1,G2 for _Graph, c,c1,c2 for Cardinal, n for Nat;
reserve f for VColoring of G;
reserve g for EColoring of G;

theorem Th120:
  G.eChromaticNum() c= G.size()
proof
  G is G.size()-ecolorable & G.size() c= G.size() by Th100;
  then G.size() in EColSet(G);
  hence G.eChromaticNum() c= G.size() by SETFAM_1:3;
end;
