proposition: Lemma Derivative_minus : Derivative I pI (F{-}G) (F'{-}G').
proof: Proof. elim derF; intros incF H. elim H; intros incF' derivF. elim derG; intros incG H'. elim H'; intros incG' derivG. split. Included. split; Deriv. Qed.
imports: CoRN.ftc.MoreIntervals