D = (2, 4)
C = (6, 4)
A = (1, 1)
B = (5, 1)
a = Segment(D, C)
b = Segment(C, B)
c = Segment(B, A)
d = Segment(A, D)
Z = (-2.48, 1.64)
k = 1 (slider from -5 to 5, step 0.1)