Haftendorn, Buch:
Kurven erkunden und verstehen
Kap 05: S. 17 Abb.2.6 

Ha 2016

θ

θ

r(x) = If[0 ≤ x ≤ (2 * π), abs(π - x) - π / 2, 0]
θ = 2 (slider from 0 to 6.283185307179586, step 0.1)
P: (r(θ); θ)
Ortslinie1 = Locus(P, θ)
K: (θ, r(θ))
T: (x(K), 0)
O = (0, 0)
a = Segment(O, P)
b = Segment(K, T)
M = (3.141592653589793, -1.5707963267948966)
M_x = (3.141592653589793, 0)
S = (0, 1.5707963267948966)
B = (1.5707963267948966, 0)
c = Segment(O, B)
P_n = Mirror(P, O)
A = (-0.8370360339876165, 0.4296296296296325)
d = false
f = Segment(O, T)
α = Angle(B, O, P)
g = Segment(P_n, O)
β = Angle(B, O, P_n)