
theorem
  for S1,S2 being non empty ManySortedSign for v being Vertex of S1
  holds v is Vertex of S1+*S2
proof
  let S1,S2 be non empty ManySortedSign;
  let v be Vertex of S1;
  v in (the carrier of S1) \/ (the carrier of S2) by XBOOLE_0:def 3;
  hence thesis by CIRCCOMB:def 2;
end;
