End Circumcenter2.
Section Circumcenter3.
Context `{TE:Tarski_euclidean}.

(* Specifications: *)
Lemma midpoint_thales_reci_circum :
forall A B C O: Tpoint,
Per A C B ->
Midpoint O A B ->
is_circumcenter O A B C.
Lemma circumcenter_per :
forall A B C O,
A<>B -> B<>C ->
Per A B C ->
is_circumcenter O A B C ->
Midpoint O A C.