Reduce with system of equations involving D

*To*: mathgroup at smc.vnet.net*Subject*: [mg113824] Reduce with system of equations involving D*From*: Eduardo Cavazos <wayo.cavazos at gmail.com>*Date*: Sun, 14 Nov 2010 06:10:31 -0500 (EST)

Hello, Here I'm using Reduce on a system of equations to find 'a' symbolically: { \[CapitalSigma]\[Tau] == D[Subscript[m, 1]*v*R + Subscript[m, 2]*v*R + \[CapitalIota]*v/R, t, NonConstants -> {v}], \[CapitalSigma]\[Tau] == Subscript[m, 1]*g*R, a == D[v, t, NonConstants -> v], Subscript[m, 1] > 0, Subscript[m, 2] > 0, g > 0, R > 0, \[CapitalIota] > 0 } Reduce[%, {a, D[v, t, NonConstants -> v], \[CapitalSigma]\[Tau]}] The answer is correct. However, I had to simplify the set of equations slightly. I'd like to say that: \[CapitalSigma]\[Tau] == D[L[t], t] where: L == Subscript[m, 1]*v*R + Subscript[m, 2]*v*R + \[CapitalIota]*v/R So something like this (Just to give you an idea. This doesn't produce the right answer.): { L == Subscript[m, 1]*v*R + Subscript[m, 2]*v*R + \[CapitalIota]*v/R, \[CapitalSigma]\[Tau] == D[L[t], t], \[CapitalSigma]\[Tau] == Subscript[m, 1]*g*R, a == D[v, t, NonConstants -> v], Subscript[m, 1] > 0, Subscript[m, 2] > 0, g > 0, R > 0, \[CapitalIota] > 0 } Reduce[%, {a, D[v, t, NonConstants -> v], \[CapitalSigma]\[Tau]}] Thanks for any suggestions. Ed