RE: Re: Getting rid of the symbol -> after finding the root

*To*: mathgroup at smc.vnet.net*Subject*: [mg39350] RE: [mg39326] Re: Getting rid of the symbol -> after finding the root*From*: "David Park" <djmp at earthlink.net>*Date*: Wed, 12 Feb 2003 03:52:38 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Mostaghel, Mathematica almost always returns the results of various "solving" routines as a set of rules. Often there may be multiple variables and/or multiple values and then you get sets of rules. You could save the rules and use them later to substitute into some expression. Here is an example. xsol = FindRoot[Cos[x] == x, {x, 1}] {x -> 0.739085} I saved the rule in the variable xsol. Then suppose you have an expression in x. You can replace using xsol. x^2 + 2x - 3 % /. xsol -3 + 2*x + x^2 -0.975583 /. is the shortcut for ReplaceAll. (Lookup ReplaceAll in Help. Also lookup Rule.) It uses the rule to replace each value of x. Or you could replace x and save it once and for all. Clear[x]; FindRoot[Cos[x] == x, {x, 1}] x = x /. % {x -> 0.739085} 0.739085 Now everytime you use x in an expression it will be replaced by its value. x^2 + 2x - 3 -0.975583 I like the first procedure a little better because I don't like to assign permanent values to a symbol like x. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Mostaghel, Naser [mailto:NMostag at UTNet.UToledo.Edu] To: mathgroup at smc.vnet.net Dear Friends, I need to use the root of a simple equation in subsequent operations. After extracting the root, it comes in the form ->root. I have not been able to get rid of the symbol -> . Can someone help? Thanks, Naser Mostaghel Professor, Civil Engineering T: (419) 530-8131 F: (419) 530-8116 E: nmostag at utnet.utoledo.edu