unfold sqrd.
apply mult_le_compat; auto.
Qed.
Hint Resolve sqrd_plus sqrd_le.
(* div2 properties *)

(* Specifications: *)
Lemma div2_preserves_le x y: x <= y -> div2 x <= div2 y.
Lemma Sdiv2_eq_div2SS x: S (div2 x) = div2 (S (S x)).
Lemma div2_x_plus_Sx b: div2 (b + S b) = b.
Proof with auto with arith.