Section Quadrilateral_inter_dec_2D.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma perp3__perp :
forall A B C D,
Perp A B B C ->
Perp B C C D ->
Perp C D D A ->
Perp D A A B.