theorem Th10:
  for f1,f2 be XFinSequence,n st n <= len f1 holds
   (f1^f2)/^n = (f1/^n)^f2
proof
  let f1,f2 be XFinSequence,n;
  assume n <= len f1; then
  A2: len (f1|n) = n by AFINSQ_1:54;
  f1 = (f1|n)^ (f1/^n);
  then f1^f2 = (f1|n)^ ((f1/^n)^f2) by AFINSQ_1:27;
  hence (f1^f2)/^n = ((f1/^n)^f2) by A2,AFINSQ_2:12;
end;
