Question for Partial differential summationseries

*To*: mathgroup at smc.vnet.net*Subject*: [mg122801] Question for Partial differential summationseries*From*: dai <dahfsys at gmail.com>*Date*: Fri, 11 Nov 2011 04:52:55 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

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.

**Follow-Ups**:**Re: Question for Partial differential summationseries***From:*Ralph Dratman <ralph.dratman@gmail.com>

**Re: Question for Partial differential summationseries***From:*DrMajorBob <btreat1@austin.rr.com>