Proving a relation between cross and dot products

Bipolarity
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Another vector identity I have been trying to prove. My textbook lists this identity in "properties of cross products" without proving it. I have been trying to prove it, withou much luck, so some insight is appreciated.

u \times (v \times w) = (u \cdot w)v - (u \cdot v)w

Thanks!

BiP
 
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This belongs in the homework section.
 

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