∡ BEC = (sđ BC - sđ AD)/2

O = (35.088428321678315, -0.056351981351984964)
B_1 = (37.55580011655011, -2.038339160839164)
c = Circle(O, B_1)
E = (37.394005244755235, 4.514353146853142)
B = Point(c)
C = Point(c)
a = Ray(E, B)
b = Ray(E, C)
A = Intersect(c, a, 2.0)
D = Intersect(c, b, 2.0)
d = Segment(A, C)
α = Angle(B, A, C)
β = Angle(B, E, C)