A = Point(yAxis)
B = Point(xAxis)
a = Ray(A, B)
C = Point(yAxis)
c = Circle(C, 1.0)
D = Intersect(c, a, 1.0)
D' = Rotate(D, 240.00000000000003°, C)
α = Angle(D, C, D')
b = Ray(C, D')
β = Angle(b, xAxis)
γ: β - 180.0 * °