In this paper, we discuss the role of a circular part of radial-circular networks. To simplify the problem, we consider two radial lines which intersects at a center by angle theta, and a circular arc which connects the two lines and has radius r from the center. Assuming that the activity densities along the radial lines are given, we can calculate the functions of the circular arc which has r and theta. From these calculations, some useful results have been obtained.
