Ltac ang_instance a A B C :=
  assert(tempo_ang:= ex_points_ang a);
  match goal with
    |H: Q_CongA a |-  _ => assert(tempo_H:=H); apply tempo_ang in tempo_H;
                       elim tempo_H; intros A ; let tempo_HP := fresh "tempo_HP" in intro tempo_HP; clear tempo_H;
                       elim tempo_HP; intro B; let tempo_HQ := fresh "tempo_HQ" in intro tempo_HQ ; clear tempo_HP ;
                       elim tempo_HQ; intro C; intro;  clear tempo_HQ
  end;
  clear tempo_ang.

(* Specifications: *)
Lemma ang_conga : forall a A B C A' B' C', Q_CongA a -> a A B C -> a A' B' C' -> CongA A B C A' B' C'.
Lemma is_ang_conga : forall A B C A' B' C' a, Ang A B C a -> Ang A' B' C' a -> CongA A B C A' B' C'.
Lemma is_ang_conga_is_ang : forall A B C A' B' C' a, Ang A B C a -> CongA A B C A' B' C' -> Ang A' B' C' a.
Lemma not_conga_not_ang : forall A B C A' B' C' a , Q_CongA a -> ~(CongA A B C A' B' C') -> a A B C -> ~(a A' B' C').
Lemma not_conga_is_ang : forall A B C A' B' C' a , ~(CongA A B C A' B' C') -> Ang A B C a -> ~(a A' B' C').
Lemma not_cong_is_ang1 : forall A B C A' B' C' a , ~(CongA A B C A' B' C') -> Ang A B C a -> ~(Ang A' B' C' a).
Lemma ex_eqa : forall a1 a2, (exists A , exists B, exists C, Ang A B C a1 /\ Ang A B C a2) -> EqA a1 a2.
Lemma all_eqa : forall A B C a1 a2, Ang A B C a1 -> Ang A B C a2 -> EqA a1 a2.
Lemma is_ang_distinct : forall A B C a , Ang A B C a -> A <> B /\ C <> B.
Lemma null_ang : forall A B C D a1 a2, Ang A B A a1 -> Ang C D C a2 -> EqA a1 a2.
Lemma flat_ang : forall A B C A' B' C' a1 a2, Bet A B C -> Bet A' B' C' -> Ang A B C a1 -> Ang A' B' C' a2 -> EqA a1 a2.
Lemma ang_distinct: forall a A B C, Q_CongA a -> a A B C -> A <> B /\ C <> B.
Lemma ex_ang : forall A B C, B <> A -> B <> C -> exists a, Q_CongA a /\ a A B C.
Lemma anga_exists : forall A B C, A <> B -> C <> B -> Acute A B C -> exists a, Q_CongA_Acute a /\ a A B C.
Lemma anga_is_ang : forall a, Q_CongA_Acute a -> Q_CongA a.
Lemma ex_points_anga : forall a , Q_CongA_Acute a -> exists A, exists B, exists C, a A B C.