proposition: Theorem wB_div2: forall x, wB/2 <= x -> wB <= 2 * x.
proof: Proof. intros x H; rewrite <- wB_div_2; apply Z.mul_le_mono_nonneg_l; zarith. Qed.
imports: ZArith Lia BigNumPrelude DoubleType DoubleBase DoubleDivn1 DoubleAdd DoubleSub