
theorem Th7:
  for S,T being RelStr, f being Function of S,T st f is one-to-one
  for R being SubRelStr of S holds f|R is one-to-one
proof
  let S,T be RelStr, f be Function of S,T such that
A1: f is one-to-one;
  let R be SubRelStr of S;
  f|R = f|the carrier of R by Th6;
  hence thesis by A1,FUNCT_1:52;
end;
