Require Export GeoCoq.Tarski_dev.Ch13_6_Desargues_Hessenberg.
Section T14_sum.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

(* Specifications: *)
Lemma Pj_exists : forall A B C,
exists D, Pj A B C D.
Lemma sum_to_sump : forall O E E' A B C, Sum O E E' A B C -> Sump O E E' A B C.
Lemma sump_to_sum : forall O E E' A B C, Sump O E E' A B C -> Sum O E E' A B C.
(* a inclure dans project.v *)
Lemma project_col_project : forall A B C P P' X Y,
A <> C -> Col A B C ->
Proj P P' A B X Y ->
Proj P P' A C X Y.