Question: Create A Unit Vector of a 3d Vector

I have a simple question, but don't find a neat solution for it. I have 4 3d Vectors that result in the resulting Vector V5. I now want the unit vector of V5. How do I do it the most efficient way? 

My attempt is in the file attached. I get the error message: "Error, (in rtable/Power) exponentiation operation not defined for Vectors"

Thanks a lot for your help.3d_vector.mw

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