Differentiate into a sum



On 02/07/07, sen1 at math.msu.edu <sen1 at math.msu.edu> wrote:
> Are the expressions
>    x[k]
> independent?

Yes.

> You say "some function" of the sum.
>
> Is this just the composition
>
> g(u)
>
> where
>   u = sum(a[k]*x[k])
>
> where   a   and    x    are just vectors?

Well, yes, but in fact I want something more than just something quite
so simple as an inner product. It was just an example. But I would be
happy if Maxima could do just that.

> In that case,  du/d(x[k]) is just a[k], so perhaps

Yes, I'm aware, but I would like Maxima to know that du/dx[k] is a[k]
without me telling it.

That's about the extent of what I would like Maxima to do. Even for
this simple example, that would be enough.

- Jordi G. H.