Cross Product Proof: u X v X w = u X (v X w)

[MJC684]

Homework Statement

(u X v) X w = u X (v X w) Iff (u X w) X v = 0

Homework Equations

(u X v) = -(v X u)

The Attempt at a Solution

I know that I am supposed to prove this by proving P --> Q and Q --> P
I know that if (u X w) X V = 0 then (u X w) is a scalar multiple of v.

How do i deduce Q from P and P from Q?

 

[tiny-tim]

Hi MJC684!

What is (u X v) X w - u X (v X w) ?

(use the Einstein summation convention if you know it, otherwise use coordinates)