rewrite <- (Zpower_nat_O radix); rewrite pGivesBound; auto with zarith.
Qed.

Theorem PosNormMin : Zpos (vNum b) = (radix * nNormMin)%Z.
pattern radix at 1 in |- *; rewrite <- (Zpower_nat_1 radix);
unfold nNormMin in |- *.