(* Gabriel Braun March 2013 *)
Require Export GeoCoq.Tarski_dev.Annexes.vectors.
Section Projections.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma project_preserves_bet :
forall A B X Y P Q R P' Q' R',
Bet P Q R ->
Proj P P' A B X Y ->
Proj Q Q' A B X Y ->
Proj R R' A B X Y ->
Bet P' Q' R'.