d = 6 Pi/99; Manipulate[ Graphics[{ { If[4 Pi >= s > 2 Pi, { Darker@Red, Table[ Block[{p}, p = {Sin[t], Cos[t]}; Circle[p, Norm[{0, 1} - p]]] , {t, 2 Pi, Max[2 Pi + 0.01, s], d}] } , If[4 Pi < s, { Darker@Red, Table[ Block[{p}, p = {Sin[t], Cos[t]}; Circle[p, Norm[{0, 1} - p]]] , {t, s, 6 Pi, d}] } , {} ] ], Thickness[0.01], Circle[{0, 0}, 1], Circle[{Sin[s], Cos[s]}, Norm[{0, 1} - {Sin[s], Cos[s]}]] }, Darker@Red, PointSize[Large], Point[{Sin[s], Cos[s]}], Line[{{0, 1}, {Sin[s], Cos[s]}}] }, PlotRange -> 3.1, ImageSize -> 220] , {s, 0, 6 Pi, d}]