From the tangent lines, a series of circles is derived (the number of circles that can be derived equals n|/(3|*(n-3)|) or n C3 where n is the number of lines or points, e.g. for 1 line, 0 circles; for 2 lines, 0 circles; for 3 lines, 1 circle; for 4 lines, 4 circles; for 5 lines, 10 circles . . . ).