A = Point(yAxis)
B = (0, -2)
a = Segment(A, B)
head = 3.141592653589793 rad (slider from 140*° to 220*°, step 0.08726646259971647)
C = Point(a)
D = Point(a)
C' = Rotate(C, head, A)
β = Angle(C, A, C')
c = Circle(C', 0.5)