theorem Th82:
  for F being Function of [:D,D9:],E for p being FinSequence of D
  st r = F[:](p,d9) holds len r = len p
proof
  let F be Function of [:D,D9:],E;
  let p be FinSequence of D;
  rng p c= D by FINSEQ_1:def 4;
  then [:rng p,{d9}:] c= [:D,D9:] by ZFMISC_1:96;
  then [:rng p,{d9}:] c= dom F by FUNCT_2:def 1;
  hence thesis by Th67;
end;
