reserve i, j, k, l, m, n, t for Nat;

theorem
  k <= n implies (2 to_power n) div (2 to_power k) = 2 to_power (n -' k)
proof
  assume k <= n;
  then 2 to_power k > 0 & 2 to_power n = (2 to_power k) * (2 to_power (n-'k))
  by Th10,POWER:34;
  hence thesis by NAT_D:18;
end;
