intro.
apply H.
eapply cong_identity.
apply H0.
Qed.

(* Specifications: *)
Lemma midpoint_col : forall A B A' B' M, A <> B -> Midpoint M A A' -> Midpoint M B B' -> Col A B B' -> A' <> B' /\ Col A A' B' /\ Col B A' B'.
intros.