theorem
  for F being Function of [:D,D9:],E for p being FinSequence of D for p9
  being FinSequence of D9 holds F.:(<*>D,p9) = <*>E & F.:(p,<*>D9) = <*>E
proof
  let F be Function of [:D,D9:],E;
  let p be FinSequence of D;
  let p9 be FinSequence of D9;
  reconsider r = F.:(<*>D,p9),r9 = F.:(p,<*>D9) as FinSequence of E by Th68;
  len(<*>D) = 0;
  then len r = min(0,len p9) & len r9 = min(len p,0) by Th69;
  hence thesis by XXREAL_0:def 9;
end;
