proposition: Lemma conga_isosceles : ~ Col A B C -> CongA C A B A C B -> isosceles A B C.
proof: Proof. intros. assert (Cong B A B C) by (apply l11_44_1_b;finish;CongA). unfold isosceles. Cong. Qed.
imports: GeoCoq.Tarski_dev.Ch12_parallel GeoCoq.Tarski_dev.Annexes.perp_bisect