Re: DSolve problems with system of ODEs. Out in pure notation?

*To*: mathgroup at smc.vnet.net*Subject*: [mg21725] Re: DSolve problems with system of ODEs. Out in pure notation?*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Wed, 26 Jan 2000 03:45:28 -0500 (EST)*Organization*: Universitaet Leipzig*References*: <200001210900.EAA06601@smc.vnet.net> <200001220753.CAA11688@smc.vnet.net> <86e8o3$fbv@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, you get back a corect analytical solution ? So what's you problem ? Since you give a numerical matrix of your system and you don't like the RootSum[] objects you can simply DSolve[{x'[t] == -0.036 x[t] + 0.0124 y[t] + 0.000035 z[t] + 49.3, y'[t] == 0.0111 x[t] - 0.0286 y[t], z'[t] == 0.0039 x[t] - 0.000035 z[t], x[0] == 0, y[0] == 0, z[0] == 0}, {x[t], y[t], z[t]}, t] // N force the numerical evaluation of the RootSum[]'s by N[] Hope that helps Jens "J.Guillermo Sanchez" wrote: > > If I evaluate, > > DSolve[{x'[t] == -0.036 x[t] + 0.0124 y[t] + 0.000035 z[t] + 49.3, > y'[t] == 0.0111 x[t] - 0.0286 y[t], z'[t] == 0.0039 x[t] - 0.000035 > z[t], > x[0] == 0, y[0] == 0, z[0] == 0}, {x[t], y[t], z[t]}, t] > > I receive a massage like this > (RootSum::"pfn" : > "(DSolve`DSolveDump`dysfunction$6[273147 + <<1>>... > is not a pure function.). > and them a out in pure notation. > > But I want to receive the solution in standard notation. > > Also the same sentece work fine in Mathematica 2.2. > > Can anyone give a hand?

**References**:**Intersection of 2 subspaces***From:*RENAULT Fabien <renaulf1@cti.ecp.fr>

**Re: Intersection of 2 subspaces***From:*Daniel Lichtblau <danl@wolfram.com>