
theorem Th73:
for F be FinSequence, m,n be Nat st m <= n holds len(F|m) <= len(F|n)
proof
   let F be FinSequence, m,n be Nat;
   assume m <= n; then
   F|m = F|n|m by FINSEQ_1:82;
   hence len(F|m) <= len(F|n) by FINSEQ_1:79;
end;
