Section T11_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** This is exterior angle theorem *)

Lemma l11_41 : forall A B C D,
~ Col A B C ->
Bet B A D ->
A <> D ->
LtA A C B C A D /\ LtA A B C C A D.