proposition: Lemma IMult_strext : forall x y : subset I, f x[*]g x [#] f y[*]g y -> x [#] y.
proof: Proof. intros x y H. elim (bin_op_strext_unfolded _ _ _ _ _ _ H); intro H0; exact (csf_strext_unfolded _ _ _ _ _ H0). Qed.
imports: CoRN.ftc.PartFunEquality