theorem Th76:
  for F being Function of [:D,D9:],E for p being FinSequence of D9
  st r = F[;](d,p) holds len r = len p
proof
  let F be Function of [:D,D9:],E;
  let p be FinSequence of D9;
  rng p c= D9 by FINSEQ_1:def 4;
  then [:{d},rng p:] c= [:D,D9:] by ZFMISC_1:96;
  then [:{d},rng p:] c= dom F by FUNCT_2:def 1;
  hence thesis by Th65;
end;
