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 Th11:
  for g,f being Element of Morphs(V) holds [g,f] in dom comp(V)
  iff dom(g) = cod(f)
proof
  let g,f be Element of Morphs(V);
  dom(g) = dom'(g) & cod(f) = cod'(f);
  hence thesis by Def13;
end;
