|AB| = |[0, 2, 4] - [5, 5, 0]| = |[-5, -3, 4]| = √(5^2 + 3^2 + 4^2)
|BC| = |[-5, 5, 0] - [0, 2, 4]| = |[-5, 3, -4]| = √(5^2 + 3^2 + 4^2)
AB·BC = [-5, -3, 4]·[-5, 3, -4] = 0
AD = BC
D - A = BC
D = A + BC = [5, 5, 0] + [-5, 3, -4] = [0, 8, -4]
Der Punkt D lautet damit: D(0 | 8 | -4).
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