reserve X,Y for set;
reserve Z for non empty set;

theorem Th2:
  for f being Function of X,Y st f is bijective holds f" is Function of Y,X
proof
  let f be Function of X,Y;
  assume
A1: f is bijective;
  then rng f = Y by FUNCT_2:def 3;
  hence thesis by A1,FUNCT_2:25;
end;
