
theorem Th50:
  for G1, G2 being _Graph st G1 == G2 holds G1.loops() = G2.loops()
proof
  let G1, G2 be _Graph;
  assume G1 == G2;
  then G1 is Subgraph of G2 & G2 is Subgraph of G1 by GLIB_000:87;
  then G1.loops() c= G2.loops() & G2.loops() c= G1.loops() by Th48;
  hence thesis by XBOOLE_0:def 10;
end;
