Six Circles Theorem

The construction of a circle tangent to two intersecting lines and another circle is not trivial. One has to find the intersection of the bisector and the parabola with focus the center of the first circle. So it seems there is no geometric construction. Therefore we present the analytical construction here. This might explain why this quite instructive theorem was found so late.

C. J. A. Evelyn, G. B. Money-Coutts, J. A. Tyrrell, The Seven Circles Theorem and Other New Theorems, London: Stacey International, 1974 pp. 31–42. (This booklet seems hard to find according to Seven Circles Theorem.)