Z = (-1, 1)
P = (1, 2)
Q = (1, 0)
P' = (3, 3)
Q' = (3, -1)
a = Segment(Q, P)
b = Segment(P', Q')
c = Segment(Z, Q)
d = Segment(Z, Q')
e = Segment(Z, P)
f = Segment(Z, P')