I\'m looking for a definitive answer, maybe a function cos I\'m slow, that will determine if a line segment and circle have collided, in javascript (working with canvas)
This is the basic concept if you don't know how to solve equations in general. I will leave the rest of the thinking to you. ;) Figuring out CD's length isn't that hard.
If you are asking how, that's how:
Finding collisions in JavaScript is kind of complicated.