Section HalfAngle.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
Definition HalfA P A O B := ~ Bet A O B /\ InAngle P A O B /\ CongA A O P B O P.

Lemma conga_halfa__conga1 : forall P A O B P' A' O' B',
HalfA P A O B -> HalfA P' A' O' B' ->
CongA A O P A' O' P' ->
CongA A O B A' O' B'.