Section T16.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.
(** Lemma 16.2 in dimension 2. *)
(** As we are in dimension 2, we skip 16.3 which is only needed to prove 16.4 in dimension n. *)

(** Lemma 16.10 for k  = 2. *)
Lemma cong_3_2_cong_4 : forall O E I J S U X Y,
O <> E -> Col O E I -> Col O E J ->
Cong_3 O E I S U X -> Cong_3 O E J S U Y ->
Cong_4 O E I J S U X Y.