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

Lemma l11_25 : forall P A B C A' C' P',
InAngle P A B C ->
Out B A' A ->
Out B C' C ->
Out B P' P ->
InAngle P' A' B C'.