The circle through the cusp of the arbelos and the tangent points of the first Pappus circle, which is congruent to the two Archimedes'
circles. If 
and 
,
then the radius of the Bankoff circle is
 |
Bankoff Circle
See also
Archimedes' Circles, Arbelos, Pappus ChainExplore with Wolfram|Alpha
References
Bankoff, L. "Are the Twin Circles of Archimedes Really Twins?" Math. Mag. 47, 214-218, 1974.Gardner, M. "Mathematical Games: The Diverse Pleasures of Circles that Are Tangent to One Another." Sci. Amer. 240, 18-28, Jan. 1979.Referenced on Wolfram|Alpha
Bankoff CircleCite this as:
Weisstein, Eric W. "Bankoff Circle." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BankoffCircle.html