Mittenviereck

A: (2 | -3 | 1)
B = (1, 3, 2)
C = (-3, 1, 0)
D = (2, 4, 5)
E: (A + B) / 2
F: (B + C) / 2
G: (C + D) / 2
H: (D + A) / 2
f = Segment(A, B)
g = Segment(B, C)
h = Segment(C, D)
i = Segment(D, A)
u = Vector(E, F)
a = Vector(E, H)
w = Vector(F, G)
v = Vector(H, G)