a = 16.4 (slider from 0 to 50, step 0.1)
A: (a, 0)
B: (a, 2)
c = Circle(B, A)
V = Rotate(A, ((-a)) / 2, B)
b = Segment(B, V)
C = Point(xAxis)
D = Point(xAxis)
d = Line(C, D)