On 7/1/07, Jordi Gutierrez Hermoso <jordigh at gmail.com> wrote:
> How can I do something like finding the derivative wrt to x[r] of some
> function of the sum sum(a[k]*x[k], k, 1, n)?
There is no built-in way. You could of course write code to do this,
but it wouldn't be completely trivial... consider cases like
diff( sum(x[i]*x[n-i], i, 1, n), x[3] )
or
diff( sum( sum( x[i+j], i, 0, j ), j, 0, n) ), x[3] )