reserve D for non empty set,
  f for FinSequence of D,
  p, p1, p2, p3, q for Element of D,
  i, j, k, l, n for Nat;

theorem Th10:
  1 <= k & k <= len f & k <> i implies Replace(f, i, p)/.k = f/.k
proof
  assume
A1: 1 <= k & k <= len f & k <> i;
  reconsider i,k as Element of NAT by ORDINAL1:def 12;
  k <> i & k in dom f by A1,FINSEQ_3:25;
  hence thesis by FUNCT_7:37;
end;
