Move point B to extend focus C toward infinity. What happens when line BP is parallel to line VAC? Leibniz says that when line BP is all but parallel to line VAC, angle ACB is infinitely small. But I have added line B'C which will create and angle B'CA that is always less than angle BCA. Will angle B'AC be less than angle BAC at the "transition point" when the angle (BAC or B'AC?) is infinitely small?