most recent 30 from http://mathoverflow.net 2013-05-21T09:40:47Z http://mathoverflow.net/feeds/question/70870 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/70870/circle-bitangent-angles Michael 2011-07-21T02:13:35Z 2011-07-21T02:13:35Z

<p>Say we have two circles $C_1$ and $C_2$ with radii $r_1$ and $r_2$, respectively. Let their centers be $d$ units apart. There are 4 bitangents, two outer and two inner.</p> <p>Examine the intersection of an inner bitangent with an outer one, near $C_1$. I'm looking for the value of the angle in the quadrant that contains $C_2$ in terms of $r_1,r_2$, and $d$.</p> <p>Anyone have a reference (or a solution) for this? I'm sure it's been looked at before, but I don't know where to look.</p>