Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!ctrsol!ginosko!usc!apple!turk
From: turk@Apple.COM (Ken "Turk" Turkowski)
Newsgroups: comp.graphics
Subject: Re: Tangents to three circles
Message-ID: <3828@internal.Apple.COM>
Date: 23 Aug 89 06:05:49 GMT
References: <11391@polya.Stanford.EDU>
Organization: Advanced Technology Graphics, Apple Computer, Cupertino, CA, USA
Lines: 14

I haven't worked this out, but perhaps the solution would be simpler if
solved through the use of conformal mapping in the complex plane, where
circles and lines are the same.

Specifically, find the conformal mapping that takes one of the circles
into a line, find the pencil of circles that are tangent to the two
remaining circles, then find the one circle in this pencil that is
tangent to the line.  Then, apply the inverse conformal mapping and,
voila, you have the desired circle.
-- 
Ken Turkowski @ Apple Computer, Inc., Cupertino, CA
Internet: turk@apple.com
Applelink: TURKOWSKI1
UUCP: sun!apple!turk