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From: gleicher@CS.CMU.EDU (Michael Gleicher)
Newsgroups: comp.graphics
Subject: HELP - intersection of 2 circles
Message-ID: <GLEICHER.90Nov16004901@OREO.GRAPHICS.CS.CMU.EDU>
Date: 16 Nov 90 05:49:01 GMT
Sender: gleicher@OREO.GRAPHICS.CS.CMU.EDU
Distribution: comp
Organization: School of Computer Science, Carnegie Mellon University
Lines: 13


Help! I can't seem to find a good way to do this.

I have 2 circles in the plane (x1,y1,r1) and (x2,y2,r2), I know they aren't
the same. 
I would like to know how many intersection points they have (0,1 or 2) and
where these intersection points are. I'd like an analytic solution (closed
form). I believe that one should exist, but i can't seem to work out the
geometry. Any help would be GREATLY appreciated (a reference, a sketch of a
proof, an equation, some C code, ...). 

Thanks,
	Mike