theorem Th68:
  for F being Function of [:D,D9:],E for p being FinSequence of D
  for q being FinSequence of D9 holds F.:(p,q) is FinSequence of E
proof
  let F be Function of [:D,D9:],E;
  let p be FinSequence of D;
  let q be FinSequence of D9;
A1: rng(F.:(p,q)) c= rng F by RELAT_1:26;
  rng p c= D & rng q c= D9 by FINSEQ_1:def 4;
  then [:rng p,rng q:] c= [:D,D9:] by ZFMISC_1:96;
  then [:rng p,rng q:] c= dom F by FUNCT_2:def 1;
  then
A2: F.:(p,q) is FinSequence by Th62;
  rng F c= E by RELAT_1:def 19;
  then rng(F.:(p,q)) c= E by A1;
  hence thesis by A2,FINSEQ_1:def 4;
end;
