a)
C = A + AC = [3, 1, -2] + [-3, 1, 9] = [0, 2, 7]
D = B + BD = [-2, 5, 3] + [5, -5, -1] = [3, 0, 2]
b)
AB = B - A = [-2, 5, 3] - [3, 1, -2] = [-5, 4, 5]
DC = C - D = [0, 2, 7] - [3, 0, 2] = [-3, 2, 5] → Kein Parallelogramm da AB ≠ DC
|AB| = |[-5, 4, 5]| = √66
|BC| = |[0, 2, 7] - [-2, 5, 3]| = √29
|CD| = |[-3, 2, 5]| = √38
|AD| = √17