unfold disjoint.
intro.
destruct H0 as [P []].
assert(HP:= betH_trans0 A P B C H0 H).
spliter.
apply between_only_one' in H1.
spliter.
contradiction.
Qed.

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