The Limaçon as a Conchoid of a Circle
Given is a unit circle  and a fixed point  on the circle. 
Let   be a random point on the circle, and let  be the line through  and .  
The slider  allows us to choose and fix a distance . 
The light blue points  and  are points from the line, on a distance  to . 
As   moves along the circle, the points  and  will draw  the conchoid of the circle - a Limaçon.
- Drag the slider to see how the shape of the Limaçon depends on the distance .