proposition: Lemma halfa__acute : forall P A O B, HalfA P A O B -> Acute A O P.
proof: Proof. intros P A O B HHalfa. apply nbet_sams_suma__acute with A O B. destruct HHalfa; assumption. apply halfa__sams with B; assumption. apply halfa__suma; assumption. Qed.
imports: GeoCoq.Tarski_dev.Annexes.suma