Section T15.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.
(** Lemma 15.2 *)
(** Cong corresponds to length equality.*)
(** Le corresponds to length inequality.*)
(********************************************************)

Lemma square_increase_strict : forall O E E' A B A2 B2, Ar2 O E E' A B A ->  Ps O E A -> Ps O E B
-> LtP O E E' A B
-> Prod O E E' A A A2 -> Prod O E E' B B B2
-> LtP O E E' A2 B2.