( first of all, i apologize if this thread should be under another sub-forum, like the Analysis, Topology and Differential Geometry, but it is a very conceptual problem that might be too insignificant for that forum )
Considering this animation, i can't see how the length of the radius is determined in the terminal stage, where the 3 points overlap. Since there are 3 overlapping lines (the normals to the curve), we don't have an intersection of lines, so i don't get how the end point of the radius (meaning the center of the circle) is determined...
Secondary Question: how is that animation valid when the curve used as example isn't symmetrical anymore to the normal of the given point (and therefore the 3 normals aren't concurrent anymore)
thanks for the interest!