
theorem Th6:
  for X,Y,Z being TopStruct, f being Function of X,Y, h being
  Function of Y,Z st h is being_homeomorphism & f is one-to-one holds h*f is
  one-to-one
proof
  let X,Y,Z be TopStruct, f be Function of X,Y, h be Function of Y,Z;
  assume that
A1: h is being_homeomorphism and
A2: f is one-to-one;
  h is one-to-one by A1,TOPS_2:def 5;
  hence thesis by A2;
end;
