theorem Th70:
  for f,g being PartFunc of X,Y st g in TotFuncs(f) holds g is total
proof
  let f,g be PartFunc of X,Y;
  assume g in TotFuncs(f);
  then
  ex g9 being PartFunc of X,Y st g9 = g & g9 is total & f tolerates g9 by Def5;
  hence thesis;
end;
