Re: Can Mathematica 4 do this?

*To*: mathgroup at smc.vnet.net*Subject*: [mg24528] Re: Can Mathematica 4 do this?*From*: mend0070 at garnet.tc.umn.edu (Philip C Mendelsohn)*Date*: Mon, 24 Jul 2000 03:04:08 -0400 (EDT)*Organization*: University of Minnesota, Twin Cities Campus*References*: <8l699m$sdi@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hyun Go (mathcunix at yahoo.com) wrote: : Hi all, : I'm trying to solve a system of 8 equations with 8 : unknowns using Solve --by simply making them into a : system of simultaneous equation and let Solve run. : However, the calculation's been running for more than : 40 mins so far and I'm still waiting (I have set : $RecursionLimit = 2000). : All 8 equations in the system are non-linear; Should I : stop trying it with Mathematica, or is there any : command more appropriate in dealing with non-linear : equations? : Thanks, I don't think that Solve will do non-linear equations. If you can write your equations in the form A . x == b, you can use a form of Newton's method to solve numerically in an iterative fashion. Subtracting b from both sides results in a vector valued function that equals 0. If you start with an initial x0, (A . x0) - b = epsilon, where epsilon is some error (i.e., not 0.) If you then solve -J deltaX = epsilon, where J is the jacobian of your function for deltaX. Then your next value of x1 == x0 + delta x . If things work out well, your x should converge. I have code for a similar problem, but am unable to include it in this post. Either e-mail me, or I will try and post it later today. Hope that helps, Phil Mendelsohn -- Lottery: a tax on people who are bad at math