reserve a,x,y for object, A,B for set,
  l,m,n for Nat;
reserve X,Y for set, x for object,
  p,q for Function-yielding FinSequence,
  f,g,h for Function;

theorem Th38:
  compose({},X) = id X
proof
  ex f being ManySortedFunction of NAT st compose({},X) = f.0 & f.0 = id X
& for i being Nat st i+1 in dom {} for g,h being Function st g = f.i
  & h = {} .(i+1) holds f.(i+1) = h*g by Def3,CARD_1:27;
  hence thesis;
end;
