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Re: Some questions about vector


Do you mean a linear combination of  vectors, like this
    v = a1*v1 + a2*v2 + ... + an*vn
where v, v1,...,vn are vectors of a vector space (e.g. R^n ) and 
a1,a2,...,an are elements of  a field
?

I don't know if exists any package that treats general vector analysis
but it sounds interesting to working around it.

Bye,

    S.

"Qi Zhang" <qzhang81 at gmail.com> ha scritto nel messaggio 
news:eu54qn$l30$1 at smc.vnet.net...
> input:
>
> Clear[f];
> f[v] = Sum[(i*v[i]), {i, 1, N}]
> D[f[v], v[i]]
>
> the output is
>
> \!\(1\/2\ N\ \((1 + N)\)\)
>
> However what I expect is i
>
> What should I do in order to get the the answer I expected?
>
> Thanks a lot.
>
> -- 
> Best,
> Qi Zhang
> 



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