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

Lemma eqv_opp_null :
forall A B,
EqV A B B A ->
A = B.