The geometric realm of circles seems an unlikely setting for a startling mathematical discovery. A staple of geometry textbooks, the circle is already the subject of myriad theorems and countless exercises.
Find the radius of a fourth circle nestled between the outer circle (radius=1) and the two inner circles (each radius=1/2). Wilks
Mathematician René Descartes found a formula relating the curvatures of four mutually tangent circles.
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