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.