theorem
  1 is_a_unity_wrt multnat & multnat is uniquely-decomposable
proof
  ex n being Element of NAT st n is_a_unity_wrt multnat by SETWISEO:def 2;
  hence 1 is_a_unity_wrt multnat by Th52,Th54,BINOP_1:def 8;
  thus thesis by Def20,Th52;
end;
