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Re: use Solve[...] result as a function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68209] Re: use Solve[...] result as a function
  • From: "Robert C. Helling" <robert at atdotde.iu-bremen.de>
  • Date: Sat, 29 Jul 2006 01:00:42 -0400 (EDT)
  • References: <eaa198$n81$1@smc.vnet.net>
  • Reply-to: helling at atdotde.de
  • Sender: owner-wri-mathgroup at wolfram.com

On Thu, 27 Jul 2006 09:33:28 +0000 (UTC), alandwehr at freesurf.ch <alandwehr at freesurf.ch> wrote:
> Hello
>
> Does anybody know how to use a result of Solve[...] as a function?
> i.e. Solve gives me the result {x->x^2}. Now I want to use the result
> as a function f[x]. How does this work.
>
> Thank you very much for your help.
>
> Ananda

Solve returns the solutions as a list of replacement rules. Say you
want want to assign the first one to f[x]. Have you tried

f[x_] := x /. Solve[equation, x][[1]]

BTW, what kind of equation are you solving where the solution for
variable x is a function of x (i.e. x^2)?

If this is a typo you might mean something like

f[x_] := y /. Solve[y^2 + x^2 == 1,y][[1]]

Robert

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