Sunday

January 22, 2017
Posted by **faizel** on Friday, December 21, 2012 at 7:57am.

- maths -
**Steve**, Friday, December 21, 2012 at 11:04amThis problem is discussed at

http://mathworld.wolfram.com/TangentCircles.html

starting at equation (17), where we see that

1/√r = 1/√4 + 1/√1

1/√r = 1/2 + 1

1/√r = 3/2

r = 4/9