Given a fixed point A and point C, moving on a fixed ellipse. For each position of C we consider the projections of A onto the tangent (B) and the normal (D) at C.

For C moving on the ellipse, the geometric locus of point B is the red line [tangential pedal] of the ellipse w.r. to A. The geometric locus of D is the green line [normal pedal] of the ellipse, with respect to the point A.