End T11_1.
Section T11_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma l11_22b :
forall A B C P A' B' C' P',
OS B P A C /\ OS B' P' A' C' /\
CongA A B P A' B' P' /\ CongA P B C  P' B' C' ->
CongA A B C A' B' C'.