trigonometric summation in maxima



I am still not getting how to do it. Here is the sample session with maxima.

(C1) realpart(nusum(j*x, j, 1, N));

                                   N (N + 1) x
(D1)                              -----------
                                        2
(C2) realpart(nusum(j*j*x, j, 1, N));

                              N (N + 1) (2 N + 1) x
(D2)                         ---------------------
                                        6
(C3) realpart(nusum(cos(j/N)*x, j, 1, N));

ERREXP1 NON-RATIONAL TERM RATIO TO NUSUM
                                  N
                                 ====
                                 \         j
(D3)                           ( >    COS(-)) x
                                 /         N
                                 ====
                                 j = 1

We can see that, D3 is left unsimplified.

Milan Lukic wrote:
> Have you tried
>   realpart(nusum(%i*j*x,j,1,N));
> 	
> Milan
> 
> 
> Kamaraju Kusumanchi [02/06/04 14:45 -0400]:
> 
>>Hi all
>>  I am interested in evaluating summation involving trigonometric terms 
>>using maxima. For example
>>
>>sum(cos(j/N), j, 1, N)
>>
>>Maxima does not give the simplified answer but gives expression 
>>involving summation sign. How to get the simplified result?
>>
>>I read the manual and came across simpsum : true flag. But this does not 
>>simplify the above expression. simpsum : true works only for Riemann 
>>kind of sums.
>>
>>Any ideas how to extend the sum function to trignometric terms also?
>>
>>thanks
>>raju
>>


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