Posted by **Jose** on Friday, April 4, 2014 at 1:16am.

The curvature of a circle with radius r is defined as Descartes’ formula gives a relationship between the curvatures of the four circles. What are Descartes’ formula and the curvature of a circle? What does the sign of the curvature of a circle mean? State Descartes’ formula and use it to verify the radius you found in part (a).