\text{ Kocka }ABCDEFGH

d = 8 (slider from 5 to 8, step 0.2)
A: (((-d)) / 2, ((-d)) / 2, -2)
k = Circle(zAxis, A)
O': (0, 0, d - 2)
O: (0, 0, -2)
u = Line(A, O)
q_{1} = Plane(zAxis, u)
q = OrthogonalLine(O, q_{1})
D, B = Intersect(q, k)
C, E = Intersect(u, k)
q1, a_1, b_{1}, c, d_{2} = Polygon(A, B, C, D)
p = OrthogonalPlane(O, zAxis)
e, F, G, H, I, stenaABGF, stenaBCHG, stenaCDIH, stenaADIF, stenaFGHI, hranaAF, hranaBG, hranaCH, hranaDI, hranaFG, hranaGH, hranaHI, hranaFI = Prism(q1, Distance[O, O'])
S = Point(hranaDI)
R = Point(hranaAF)
b = Line(R, S)
P = Point(a_1)
j = Line(P, d_{2})
L = Intersect(j, c)
l = Line(L, hranaAF)
N = Intersect(l, hranaHI)
Q: N
a = Line(P, Q)
q2, b_2, c_1, h_1, g = Polygon(B, C, H, G)
M = PointIn(q2)
a' = Line(M, a)
b' = Line(M, b)
α = Angle(b', a')