45^\circ

A = Intersect(xAxis, yAxis)
B = Point(xAxis)
pol1, f, g, h, i, C, D = Polygon(A, B, 4)
c = Circle(B, C)
j = Line(A, B)
m = Line(B, C)
E_{1} = Point(c)
d = CircleArc(B, E_{1}, C)
F = Point(d)
k = Line(B, F)
l = Line(C, k)
n = Line(F, g)
E = Intersect(l, n)
q1, b, f_1, e, c_1 = Polygon(B, F, E, C)
p = Segment(C, F)
q = Segment(F, A)
α = Angle(C, F, A)