Section PARTICULAR_ANGLES.
Definition AS0 := Angle Uu Oo Uu.
Definition Ww : Point.
Definition ASpi := Angle Uu Oo Ww.

Lemma NullAngleHalfLine : forall A B C : Point,
A <> B ->
A <> C ->
Angle B A C = AS0 ->
HalfLine A B C.