Require Export C15_Parallelogramm.
Section DISTANCE_PROPERTIES.

Lemma LSplusAss : forall A B C D E F : Point,
A <> B ->
C <> D ->
E <> F ->
LSplus (Distance A B) (LSplus (Distance C D) (Distance E F)) =
LSplus(LSplus (Distance A B)  (Distance C D)) (Distance E F).