Re: Solving a symbolic complex linear system of equation.

*To*: mathgroup at smc.vnet.net*Subject*: [mg77944] Re: Solving a symbolic complex linear system of equation.*From*: Szabolcs <szhorvat at gmail.com>*Date*: Wed, 20 Jun 2007 05:33:23 -0400 (EDT)*Organization*: University of Bergen*References*: <f58dlb$8lc$1@smc.vnet.net>

Please state the question precisely. Fo wrote: > Suppose that I want to solve symbolically a system of lienar equations > defines as: > $Ax=B$ , where A is a complex matrix, B is a complex vector and x is > the vector of the unkown. You say you want to solve A x = B. If A is invertible, the solution is x = A^-1 B. Inverse[] can be used to compute A^-1. > The elements of the A matrix (that is simmetric) are in the form > $A_{ij}e^{i phi_{ij}}$. > I tried in several ways but I couldn't define the variables $A_{ij}$ > and $ phi_{ij}$ as real. Any complex number can be written in the form A Exp[I*phi] (where A and phi are real), so I do not see the point here. Or is a '=' sign missing and you mean that all the elements are complex numbers of magnitude 1? Even if they are, the solution is still A^-1 B. Do you mean that you would like to specify that some of the variables are real when simplifying the end result? For this, look up the syntax for Simplify[], and use something similar to Simplify[Sqrt[a^2], a \[Element] Reals] to specify that a variable 'a' is real. > I tried using the package Algebra`ReIm` and to define each variable as > z/:Im[z]=0. > But it does not the wanted result and also I've already read the help > page for ComplexExpand[]. What kind of result do you expect? It would be helpful if you posted the complete problem, with some more detailed explanation. > Thank you, every suggestion will be helpful. > Fortu > >