apply Zle_Zpred.
cut (maxDiv (Fnum x) (Fdigit radix x) < Fdigit radix x); auto with zarith.
apply maxDivLt; auto.
unfold Fdigit in |- *; apply NotDividesDigit; auto.
Qed.

Theorem Fexp_le_LSB : forall x : float, (Fexp x <= LSB x)%Z.
intros x; unfold LSB in |- *.