# Vector product

1. Dec 2, 2008

### -EquinoX-

1. The problem statement, all variables and given/known data

A = -3i + 4j and B = 2i + 3j

so I want to find AxB

2. Relevant equations

3. The attempt at a solution

what I got is -9k + 8k, which is -k but the answer solution says it's -17k ?

2. Dec 2, 2008

### G01

You are missing a negative sign on the 8. Remember that when you take the cross product of two vectors, A and B, in the x-y plane you will get:

$$(A_xB_y-A_yB_x)\hat{k}$$

You are missing the minus sign in the above equation.

3. Dec 2, 2008

### G01

EDIT: This post refers to a post deleted by the OP.

The i x i and j x j terms are zero by definition. You then have:

-9(i x j)+8(j x i)

Remember that the cross product anticommutes. So if ixj=k. What does this mean for j x i?

Last edited: Dec 2, 2008
4. Dec 2, 2008

### -EquinoX-

jxi is k?

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