proposition: Lemma l11_62_unicity : forall A B C D D' P, Coplanar A B C D -> Coplanar A B C D' -> (forall E, Coplanar A B C E -> Per E D P) -> (forall E, Coplanar A B C E -> Per E D' P) -> D = D'.
proof: Proof. intros A B C D D' P HCop HCop' HD HD'. apply l8_7 with P; Perp. Qed.
imports: GeoCoq.Tarski_dev.Ch10_line_reflexivity_2