comp.graphics.algorithms

Subject: Help with bisectors

Hello,
I'm implementing a straight skeleton algorithm. Everything works well
for concave and convex polygons of lines.
The algorithm calculates many bisector lines of the polygon edges. For
example

edge1
---------------------
/ |
/ |
/ | edge2
/ |
(sorry for bad ascii arc)

Now, I need to integrate circular arcs.
The problem is that at a certain point I need to calculate the
mid-curve of a circular arc and a line, and maybe the mid-curve between
two circular arcs. For now I concentrate on first case.

the mid-curve of a circular arc and a line is the curve whose points
are at the same distance from both. I could calculate it numerically,
but I have the suspect that such curve is a cubic one, and I have no
idea how to calculate it.
I know for sure , that the problem can be simplified to "circle-line
midcurve".

The numerical solution would be too slow!
I someone needs the "images" of the problem, I could send them.

Really Thanks in advance
Thomas