Section PARALLEL_SUPERIMPOSED.

Lemma TwoPointsSecantLines : forall A B : Point, forall F F' : Figure, forall D : Line F, forall D' : Line F',
Clockwise (LineA F D) (LineB F D) A ->
~Clockwise (LineA F D) (LineB F D) B ->
F' A ->
F' B ->
SecantLines F F' D D'.