α

O = Intersect(xAxis, yAxis)
c = Circle(O, 1)
B = Intersect(c, xAxis, 2)
a = 6.22 (slider from 0 to (6 * π), step 0.01)
B' = Rotate(B, a, O)
α = Angle(B, O, B')
f = Line(O, B)
d = Circle(O, a)
C = Intersect(d, f, 2)
g = OrthogonalLine(C, f)
h = OrthogonalLine(B', g)
D = Intersect(g, h)
u = Vector(O, B')