End T13.
Section T13_2D.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma l12_16_2D : forall A1 A2 B1 B2 C1 C2 X,
Par A1 A2 B1 B2 -> Inter A1 A2 C1 C2 X -> exists Y, Inter B1 B2 C1 C2 Y.