Four circles are tangent to each other and to a triangle that surrounds them, as shown in the figure. Each of the three circles in the corners have a radius of 1 cm. What is the radius of the circle in the middle?

That equation has three positive roots: R=1.51067547264, R=0.462340147657, and R=0.0894843796967, but since the radius must be large enough to touch the triangle, the only solution is R=1.51067547264. Edited on October 21, 2003, 9:32 am