High school mathematics compulsory 4 comprehensive examination questions
8.ab=n？ 0? 5-4=0 gives n = 2, because A and B are in the same direction, so n=29.c=λa+μb=(λ+μ, μ) = (- 1, 0), so λ+μ=- 1 μ=0, so λ =-. |b|=5, | c | = 3cosa =-BC/(| c || b |) = 9/15 = 3/5, COSB =-AC/(| a | c |) = 0, COSC =-AB/(| a |).