This post concludes this series about a curious function:
The circle that encloses the grey region must have the points and on its circumference; the distance between these points will be , where is the radius of the enclosing circle. Unlike the case of , we no longer have to worry about the origin, which will be safely inside the enclosing circle.
Furthermore, this line segment will be perpendicular to the angle bisector (the dashed line above), and the center of the enclosing circle must be on the angle bisector. Using trigonometry,
We see from this derivation the unfortunate typo in the above Monthly article.