Require Export GeoCoq.Tarski_dev.Ch15_lengths.
Section T16.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma grid_exchange_axes : forall O E S U1 U2,
Cs O E S U1 U2 -> Cs O E S U2 U1.