A = (3, -2.74)
a = 6.6 (slider from 0 to 10, step 0.1)
C_1 = Circle(A, a)
C_2 = Circle(A, (15.0 - a) / 2.0)
B = Point(C_1)
C_3 = Circle(B, (15.0 - a) / 2.0)
C, D = Intersect(C_2, C_3)
poly1, b_1, a_1, c_1 = Polygon(A, C, B)