(** This is SSA congruence with a right angle *)

Lemma cong2_per2__cong_conga2 :
forall A B C A' B' C',
A<>B -> B<>C ->
Per A B C ->
Per A' B' C' ->
Cong A C A' C' ->
Cong B C B' C' ->
Cong B A B' A' /\ CongA B A C B' A' C' /\ CongA B C A B' C' A'.