Global Instance IncidLP_morphisml : Proper(EqL ==> eq ==> iff) IncidLP.Global Instance IncidLP_morphismr : Proper(eq ==> EqP ==> iff) IncidLP.

Lemma cong_trans : forall A B C D E F, Cong A B C D -> Cong C D E F -> Cong A B E F.