证(台):a×b=0,1≠0,1b≠0, ∴.sin0=0,0=0,alWb (←).aWb.0=0或π.∴.sin0=0 |a×b=alb1sin0=0. 向量积符合下列运算规律: (1)axb=-b×a. (2)分配律:(a+b)×c=d×c+b×c. (3)若伪数(2d)×b=d×(2b)=(a×b). 向量积符合下列运算规律: (1) a b b a. = − (2)分配律: (a b) c a c b c. + = + (3)若 为数 ( a) b a ( b) (a b). = = () 0, a b = | a | 0, | b | 0, sin = 0, = 0, () sin = 0 | a b |=| a || b |sin = 0. 证 a b // a b // = 0或