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

Lemma ElongatedAngleChasles : forall A B C : Point,
A <> B ->
A <> C ->
Angle B A C = ASpi ->
LSplus (Distance B A) (Distance A C) = Distance B C.