On 1/13/12, Grze? Andruszkiewicz <gandrusz at gmail.com> wrote:
> I have the following sum:
> sum((R[i]-(a*X[i]+b)*t + 1/2*(c*X[i]+d)^2*t)^2/((c*X[i]+d)^2*t), i, 1, N);
>
> which I want to differenciate wrt. a:
>
> diff(%, a);
>
> but Maxima (wxMaxima to be precise) just prints d/da <my sum>. Can I
> make it actually differentiate the sum (so because N is finite is
> should differentiate every element in the sum separately)?
Well, there isn't a built-in function to carry out that operation,
but I think it can be implemented via simplification rules
(tellsimp, defrule, etc). I think this has come up before -- take
a look at the mailing list archive.
See: http://maxima.sourceforge.net/maximalist.html
best
Robert Dodier