Sometimes you need to be able to define the angle of a circle segment. Trouble is, in Illustrator, circles are not true circles; they are ellipses shaped into circles with bezier curves.
I have written a tutorial detailing the two methods I use to define the angle of a circle segment. Download the tutorial here:
A long time ago I wrote up a tutorial to do the same using Inkscape:
It might be out of date, I haven’t checked, but it’s here just in case it’s still useful. 🙂