Four Circles are Tangent to a fifth Circle or a straight Line Iff

where is a common Tangent to Circles and .

**References**

Johnson, R. A. *Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle.* Boston, MA:
Houghton Mifflin, pp. 121-127, 1929.

© 1996-9

1999-05-26