Pedal Curve

Steve Phelps' cool pedal curves got me playing a little. (Like this one, the strophoid) This sketch does pedals for functions. The slider goes from the left edge of the window to the right. The pedal of a function f(x) with respect to a point A is the locus (path) of the foot of the perpendicular from A to the tangent to the curve as the tangency point moves along the curve. I liked sine and cosine, but parabolas, circles (or half circles) and crazier stuff all makes for beautiful pedal curves.