Your expectation is, I think, wrong.
sum(y*x[i],i,0,n) is identical in meaning with
sum(y*x[k],k,0,n) assuming i and k are "free variables" in y and x.
do you expect
diff(sum(y*x[k],k,0,n),x[i]) to also be y?
how about the specifics
diff (sum(y*x[k],k,0,5),x[12]) ?
shouldn't this be 0?
How about
diff (sum(i^2,i,0,n),i) ? the sum doesn't depend on i. it depends on n.
so the derivative is 0.
If you could specify what you mean by "such type of differentiation"
maybe you mean something else. differentiating inside a summation?
RJF
Michael Krasnik wrote:
>Hello all,
>
>I have tried to do differentiation of the summation by indexed variables:
>
>(C1) diff( sum(Y*X[i],i,0,n), Y);
>(D1) 'SUM(X[i],i,0,n)
>
>(C2) diff( sum(Y*X[i],i,0,n), X[i]);
>(D2) 'DIFF('SUM(X[i],i,0,n),X[i],1)*Y
>
>For C1 everything is OK, but I have expected as a result of C2 a constant
>value Y for 0<=i<=n.
>
>Is it possible to do such type of differentiation in Maxima or not?
>If it's possible, how can I perform this operation in Maxima?
>
>Thanks in advance.
>
>
>