a)
DS = S - D = [0, 0, 6] - [-2, -2, 0] = [2, 2, 6]
DA = A - D = [2, -2, 0] - [-2, -2, 0] = [4, 0, 0]
α = ARCCOS(([2, 2, 6]·[4, 0, 0]) / (|[2, 2, 6]|·|[4, 0, 0]|)) = 72.45°
b)
Statt AS kann man aufgrund der Symmetrie auch DS nehmen.
α = ARCSIN(([2, 2, 6]·[0, 0, 1]) / (|[2, 2, 6]|·|[0, 0, 1]|)) = 64.76°