Definition CongruentStrictTriangles (A B C A' B' C' : Point) :=
	CongruentTriangles A B C A' B' C' /\
	~Collinear A B C.

Lemma CongruentStrictTrianglesC : forall A B C A' B' C' : Point, CongruentStrictTriangles A B C A' B' C' -> Angle A C B = Angle A' C' B'.