a = 6.6 (slider from 0 to 7.5, step 0.1)
A = (2, 1)
c_1 = Circle(A, a)
B = Point(c_1)
c_2 = Circle(A, (15 - a) / 2)
c_3 = Circle(B, (15 - a) / 2)
C = Intersect(c_2, c_3, 1)
t1, c, a_1, b = Polygon(A, B, C)
p: a + b + c
A1: a
B1: p