Hi -- Thinking about the problem, where I have three circles in a closest possible packing inside an equilateral triangle. So two circles on the floor, adjacent to each other touching and a third circle placed on top so that the distances off their centers from each other are all 2R, R=Radius. What I am want to know is the size of the circle that would maximally fill in the space between the three larger circles. Any ideas? I'm thinking calculus min or maximization problem. Any references, ideas or pointers appreciated.