Section Inscribed_angle.
Context `{TE:Tarski_euclidean}.
(** The sum of the angles of a triangle is the flat angle. *)
(** If A, B and C are points on a circle where the line AB is a diameter of the circle, then the angle ACB is a right angle. *)

Lemma thales_theorem : forall A B C M,
Midpoint M A B -> Cong M A M C -> Per A C B.