SetDelayed problems with matrix operation

*To*: mathgroup at smc.vnet.net*Subject*: [mg27341] SetDelayed problems with matrix operation*From*: "SANCHEZ DE LEON, Guillermo" <gsl at fab.enusa.es>*Date*: Wed, 21 Feb 2001 03:17:23 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Given a square matrix such as A={{-3, 0, 0.05}, {0.8, -0.01, 0}, {0, 0.01, -0.05}} I wish evalute the expresion: { x1[t_], x2[t_], x3[t_]} : = MatrixExp[A t].{b1, 0, 0} I receive the message SetDelayed::"shape": "Lists{ x1[t_], x2[t_], x3[t_] } and MatrixExp[A t)] . {b1, 0, 0} are not the same shape." But it is known that when MatrixExp[A t].{b1, 0, 0} will be evaluate , given a value for t, the solution will be already a list of the same shape that Lists{ x1[t_], x2[t_], x3[t_]} For instance: MatrixExp[A t].{b1, 0, 0}/.t->3 it work fine. How it will be build the the expresion { x1[t_], x2[t_], x3[t_]} : = MatrixExp[A t].{b1, 0, 0} to be evaluated?

**Follow-Ups**:**Re: SetDelayed problems with matrix operation***From:*Tomas Garza <tgarza01@prodigy.net.mx>