Definition Inter := fun X P Q R S =>
  P<>Q /\ R <> S /\ Col X P Q /\ Col X R S /\ 
  ((exists X, Col X P Q /\ ~ Col X R S) \/ (exists X, ~ Col X P Q /\ Col X R S)).

Theorem t2_8 : forall A B C D E : Point, Bet A B C -> Bet D B E -> Cong A B D B -> Cong B C B E -> Cong A E C D.