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 SupplementBC : forall A B C D A' B' C' D' : Point, A <> C -> A' <> C' -> B <> C -> Between B A D -> Between B' A' D' -> Angle B A C = Angle B' A' C' -> Angle C A D = Angle C' A' D'.