Section SUPPLEMENTARY_ANGLES.
Definition Supplementary (alpha beta : AS) :=
exists A  : Point,  exists B  : Point,  exists C : Point,  exists D : Point,
A <> C /\ Between B A D /\ Angle B A C = alpha /\ Angle C A D = beta.

Lemma SupplementaryRec : forall A B C D : Point,
Clockwise B A C ->
Clockwise C A D ->
Supplementary (Angle B A C) (Angle C A D) ->
Between B A D.