
theorem CNX:
  for f be Function, n be Nat, m be non zero Nat holds (f|(n+m)).n = f.n
  proof
    let f be Function, n be Nat, m be non zero Nat;
    set g = f|(n+m);
    n + 0 < n + m by XREAL_1:6; then
    n in Segm (n+m) by NAT_1:44;
    hence thesis by FUNCT_1:49;
  end;
