2a

a \sqrt{ 3 } 

A = (-3.9262619592166463, -6.848266920140176)
B = (14.350141500193784, -6.80938095533292)
a_1 = Segment(A, B)
A' = Rotate(A, 329.99999999999994*°, B)
α = Angle(A', B, A)
b = Ray(B, A')
c = OrthogonalLine(A, a_1)
C = Intersect(c, b)
d = Segment(C, B)
a = Segment(C, A)
β = Angle(B, A, C)