Given is a circle [math]c(O, r)[/math], and a fixed point [math]P[/math]. This will be the pedal point. [br]Let [math] R[/math] be a random point on [math]c[/math], and line [math]t [/math] be the tangent to the circle [math]c[/math] at point  [math]R[/math].[br]The light blue point is the intersecting point of [math]t[/math] and the perpendicular through [math]P[/math] to [math]t[/math]. [br]As [math]R[/math] moves along [math]c[/math], the foot of the perpendicular (the light blue point) will draw the [i]pedal curve[/i] of the circle.[br] This curve will be a Limaçon.[br][list][br][*]Drag point [math]R[/math] along the circle or press the play button.[br][*]Move the position of [math]P[/math] : outside the circle, on the circle, or inside the circle, and see the change in the Limaçon.[br][/list]