Require Export GeoCoq.Tarski_dev.Ch14_prod.
Section Order.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma pos_opp_neg : forall O E E' A mA, Ps O E A -> Opp O E E' A mA -> Ng O E mA.