reserve x,y for set;
reserve D for non empty set;
reserve UN for Universe;
reserve R for Ring;
reserve G,H for LeftMod of R;
reserve V for LeftMod_DOMAIN of R;

theorem Th10:
  for g,f being Element of Morphs(V) st dom(g) = cod(f) holds g*f in Morphs(V)
proof
  let g,f be Element of Morphs(V);
  assume dom(g) = cod(f);
  then dom'(g) = cod'(f);
  hence thesis by Th9;
end;
