B = Point(yAxis)
O = (0, 0)
e = Line(O, B)
D = Point(e)
α = 0 rad (slider from 0 to 6.283185307179586, step 0.017453292519943295)
a: y = tan(α) x
d = Line(B, a)
A = Intersect(c, a, 2)
b = Line(A, yAxis)
C = Intersect(b, d)
f_1(x) = sqrt(4 - x²) / 2
f_2(x) = -sqrt(4 - x²) / 2
P, f, g, h, i = Polygon(O, A, C, D)