proposition: Lemma concyclic_gen_trans_1 : forall P Q R A B, ~ Col P Q R -> Concyclic_gen P Q R A -> Concyclic_gen P Q R B -> Concyclic_gen Q R A B.
proof: Proof. intros P Q R A B HNC [|] [|]; [|spliter; exfalso; apply HNC; Col..]. left. apply (concyclic_trans_1 P); assumption. Qed.
imports: GeoCoq.Tarski_dev.Ch12_parallel