## Calculus (3rd Edition)

(a) $0$. (b) $0$.
(a) It is clear that the cross product of a vector and itself is zero, that is, $$\langle 4,8,2\rangle\times \langle 4,8,2\rangle =0.$$ (a) It is clear that the cross product of a vector and its multiple is zero, that is, $$\langle 4,8,2\rangle\times \langle 2,4,1\rangle =2\langle 2,4,1\rangle\times \langle 2,4,1\rangle =0.$$