case (Rmult_integral _ _ H'); simpl in |- *; auto.
case x; simpl in |- *.
intros Fnum1 Fexp1 H'0; red in |- *; simpl in |- *; auto with real zarith.
apply eq_IZR_R0; auto.
intros H'0; Contradict H'0; apply powerRZ_NOR; auto with real zarith.
Qed.

Theorem NisFzeroComp :
forall x y : float, ~ is_Fzero x -> x = y :>R -> ~ is_Fzero y.