proposition: Lemma Py_triv_ABB : forall A B, Py A B B =F= 0.
proof: Proof. intros. unfold Py, square_dist. decompose_coordinates;simpl. ring. Qed.
imports: Description Ring Field Nsatz Rtauto GeoCoq.Tarski_dev.Ch16_coordinates GeoCoq.Tarski_dev.Ch15_pyth_rel GeoCoq.Tarski_dev.Annexes.midpoint_theorems