What-If-Not Conic Constructions #5

What if the directrix in the parabola construction was NOT a line, but instead, was a circle? [br]Drag point A or point B to change the directrix into a circle. Everything in this construction is exactly the same as in the traditional parabola construction, except the directrix is a circle![br][br]Is the resulting locus still a parabola?

Information: What-If-Not Conic Constructions #5