proposition: Lemma sum_col: forall A B C, Sum O E E' A B C -> Col O E C.
proof: Proof. intros; unfold Sum, Ar2 in *; spliter; Col. Qed.
imports: Description Ring Field Nsatz Rtauto GeoCoq.Tarski_dev.Ch16_coordinates GeoCoq.Tarski_dev.Ch15_pyth_rel GeoCoq.Tarski_dev.Annexes.midpoint_theorems