reserve a,b,p,x,x9,x1,x19,x2,y,y9,y1,y19,y2,z,z9,z1,z2 for object,
   X,X9,Y,Y9,Z,Z9 for set;
reserve A,D,D9 for non empty set;
reserve f,g,h for Function;
reserve A,B for set;
reserve x,y,i,j,k for object;

theorem Th87:
  for f,g,h being Function st f c= h & g c= h holds f +* g c= h
proof
  let f,g,h be Function;
  assume f c= h & g c= h;
  then
A1: f \/ g c= h by XBOOLE_1:8;
  f +* g c= f \/ g by Th29;
  hence thesis by A1;
end;
