theorem Th66:
  for F being Injections_family of b,I st dom f = b holds f*F is
  Injections_family of cod f,I
proof
  let F be Injections_family of b,I;
  assume dom f = b;
  then cods F = I--> dom f by Def16;
  hence cods(f*F) = I --> cod f by Th17;
end;
