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

Lemma opp_pos_neg : forall O E E' A MA, Ps O E A ->  Opp O E E' A MA -> Ng O E MA.