Section Length_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Notation "l1 =l= l2" := (EqL l1 l2) (at level 80, right associativity).
Global Instance eqL_equivalence : Equivalence EqL.

Lemma ex_eqL : forall l1 l2, Q_Cong l1 -> Q_Cong l2 -> (exists A, exists B, l1 A B /\ l2 A B) -> EqL l1 l2.