Parallelstrahlen zeigen

Öffnungsweite = 0.1 (slider from 0.05 to 1, step 0.01)
p: y = Öffnungsweite x^(2)
F = Focus(p)
P = Point(p)
t = Tangent(P, p)
c = Segment(P, F)
B = Midpoint(c)
u = Vector(P, B)
C: P + (0, Length[u])
d = Ray(P, C)
A' = Mirror(P, C)
v = Vector(A', C)
D = Midpoint(B, C)
e = Segment(P, D)
α = Angle(d, e)
β = Angle(D, P, F)
text1: "α = β = " + α
list1 = Sequence((i, Öffnungsweite i^(2)), i, -15, 15)
list2 = Sequence(Ray[Element[list1, i], -v], i, 1, 31)
list3 = Sequence(Segment[Element[list1, i], F], i, 1, 31)
b = true
text2: "Brennweite = " + (y(F))
A: F + 0.3 u
a = Segment(F, A)