unfold Cong in *.
induction H.
left; intuition.
apply congH_sym.
assumption.
assumption.
right.
tauto.
Qed.

Lemma betH_congH3_outH_betH : forall A B C A' B' C',
BetH A B C -> outH A' B' C' -> CongH A C A' C' -> CongH A B A' B' -> BetH A' B' C'.