Are there 2 circles? r for the radius of the inside circle and R for the big circle? I think your question is a little unclear. I think I can help if you give more details
The result, called Euler's Theorem (in Geometry), or the Euler Triangle Formula, is proved very well at the first of the two following reference links.
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Are there 2 circles? r for the radius of the inside circle and R for the big circle? I think your question is a little unclear. I think I can help if you give more details
The result, called Euler's Theorem (in Geometry), or the Euler Triangle Formula, is proved very well at the first of the two following reference links.
http://en.wikipedia.org/wiki/Euler_inequality
http://mathworld.wolfram.com/EulerTriangleFormula....
Note that you can click on the picture at the right to see a larger version.