A = (4.7, -2.42)
B = Point(Circle[A, 4.9])
a = Segment(A, B)
c = Circle(B, 11.9)
d = Circle(A, 12.9)
C, D = Intersect(c, d)
poly1, a_1, d_1, b = Polygon(D, B, A)
α = Angle(D, B, A)