       Re: Question for Partial differential summationseries

• To: mathgroup at smc.vnet.net
• Subject: [mg122842] Re: Question for Partial differential summationseries
• From: Bill Rowe <readnews at sbcglobal.net>
• Date: Sat, 12 Nov 2011 07:33:40 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

```On 11/11/11 at 4:52 AM, dahfsys at gmail.com (dai) wrote:

>The function defined as follow

>x = X[t];
>y = Y[i, t];
>p = P[i, xv];
>w = Sum[y*p, {i, 1, N}];

>When we excuted partial differential "w" by "y" the exact solution
>is "p" (or P[i, xv]).

>However, the solution in Mathematica package is Sum[p, {i, 1, N}].

>How can I obtain the correct solution? please help.

I cannot reproduce your result. That is I get:

In:= x = X[t];
y = Y[i, t];
p = P[i, xv];
w = Sum[y*p, {i, 1, N}];
D[w, y]

Out= Sum[P[i, xv], {i, 1, N}]

In:= \$Version

Out= 8.0 for Mac OS X x86 (64-bit) (October 5, 2011)

```

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