(* Specifications: *)
Lemma l5_1 : forall A B C D, A<>B -> Bet A B C -> Bet A B D -> Bet A C D \/ Bet A D C.
Lemma l5_2 : forall A B C D, A<>B -> Bet A B C -> Bet A B D -> Bet B C D \/ Bet B D C.
Lemma l5_3 : forall A B C D, Bet A B D -> Bet A C D -> Bet A B C \/ Bet A C B.
Lemma l4_2 : forall A B C D A' B' C' D', IFSC A B C D A' B' C' D' -> Cong B D B' D'.
Lemma l4_3 : forall A B C A' B' C', Bet A B C -> Bet A' B' C' -> Cong A C A' C' -> Cong B C B' C' -> Cong A B A' B'.
Lemma cong_reflexivity : forall A B : Point, Cong A B A B.
Lemma cong_symmetry : forall A B C D : Point, Cong A B C D -> Cong C D A B.
Lemma beetween_trivial : forall A B : Point, Bet A B B.
Lemma between_symmetry : forall A B C : Point, Bet A B C -> Bet C B A.
Lemma beetween_trivial2 : forall A B : Point, Bet A A B.
Lemma between_egality : forall A B C : Point, Bet A B C -> Bet B A C -> A = B.
Lemma between_inner_transitivity : forall A B C D, Bet A B D -> Bet B C D -> Bet A B C.
Lemma between_exchange3 : forall A B C D, Bet A B C -> Bet A C D -> Bet B C D.
Lemma outer_transitivity_between2 : forall A B C D, Bet A B C -> Bet B C D -> B<>C -> Bet A C D.
Lemma between_exchange2 : forall A B C D, Bet A B D -> Bet B C D -> Bet A C D.
Lemma outer_transitivity_between : forall A B C D, Bet A B C -> Bet B C D -> B<>C -> Bet A B D.
Lemma between_exchange4 : forall A B C D, Bet A B C -> Bet A C D -> Bet A B D.