# Math Help - cross product question of j ,k ..

1. ## cross product question of j ,k ..

http://i26.tinypic.com/27zdaiv.gif

i know that i should do right hand rule to know the result
but here the vectors are weird

??

2. Originally Posted by transgalactic
http://i26.tinypic.com/27zdaiv.gif

i know that i should do right hand rule to know the result
but here the vectors are weird

??
Use this general formula:
$(a\vec{i}+ b\vec{j}+ c\vec{k})\times(u\vec{i}+ v\vec{j}+ w\vec{k})
= (bw- cv)\vec{i}+ (cu- aw)\vec{j}+ (av- bu)\vec{k}$

which can be remembered more easily by thinking of it as a "determinant":
$= \left|\begin{array}{ccc}\vec{i} & \vec{j} & \vec{k} \\ a & b & c \\ u & v & w\end{array}\right|$