theorem Th35:
  f is one-to-one implies dom(f"*f) = dom f & rng(f"*f) = dom f
proof
  assume
A1: f is one-to-one;
  then
A2: rng f = dom(f") by Th32;
  then rng(f"*f) = rng(f") by RELAT_1:28;
  hence thesis by A1,A2,Th32,RELAT_1:27;
end;
