End DerivableRulesFromSequentCalculus.
Section DerivableRulesFromAxiomatization2.
Context {L: Language}
{minL: MinimunLanguage L}
{pL: PropositionalLanguage L}
{Gamma: ProofTheory L}
{minAX: MinimunAxiomatization L Gamma}
{ipGamma: IntuitionisticPropositionalLogic L Gamma}
{cpGamma: ClassicalPropositionalLogic L Gamma}.

(* Specifications: *)
Lemma impp2orp: forall (x y: expr),
|-- (x --> y) <--> (~~ x || y).