End Circumcenter.
(* TODO investigate bug Hint Resolve/Section *)
Hint Resolve
is_circumcenter_perm_1
is_circumcenter_perm_2
is_circumcenter_perm_3
is_circumcenter_perm_4
is_circumcenter_perm_5 : Circumcenter.
Hint Resolve is_circumcenter_cop : cop.
Section Circumcenter2 .
Context `{TE:Tarski_euclidean}.
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Lemma circumcenter_perp : forall A B C A' G,
A<>B -> B<>C -> A<>C -> G <> A' ->
is_circumcenter G A B C ->
Midpoint A' B C ->
Perp_bisect G A' B C.