Archimedean circle

If the arbelos is normed such that the diameter of its outer (largest) half circle has a length of 1 and r denotes the radius of any of the inner half circles, then the radius ρ of such an Archimedean circle is given by There are over fifty different known ways to construct Archimedean circles.

[1] An Archimedean circle was first constructed by Archimedes in his Book of Lemmas.

In his book, he constructed what is now known as Archimedes' twin circles.

Woo considered the Schoch line, and with it, he was able to create a family of infinitely many Archimedean circles known as the Woo circles.

[6] In 1831, Nagata (永田岩三郎遵道) proposed a sangaku problem involving two Archimedean circles, which are denoted by W6 and W7 in [3].

In 1853, Ootoba (大鳥羽源吉守敬) proposed a sangaku problem involving an Archimedean circle.