Section Projections.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma project_par_eqv :
forall P P' Q Q' A B X Y,
Proj P P' A B X Y ->
Proj Q Q' A B X Y ->
Par P Q A B ->
EqV P Q P' Q'.