Limaçon as a Pedal of a Circle

Given is a circle , and a fixed point . This point will be the pedal point. Let be a random point on , and let the line be tangent to the circle at point .
  • Click the button to complete the construction.
The green point is the intersecting point of and the perpendicular to through . As moves over , the foot of the perpendicular (the green point) will draw the pedal curve of the circle. This curve will be a . Move the position of : outside the circle, on the circle, or inside the circle, and see the change in the Limaçon.