Definition CongruentTriangles (A B C A' B' C' : Point) :=
	Distance A B = Distance A' B' /\
	Distance B C = Distance  B' C' /\
	Distance C A = Distance C' A'.

Lemma CongruentTrianglesBC : forall A B C A' B' C' : Point, CongruentTriangles A B C A' B' C' -> Distance B C = Distance B' C'.