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RE: Solving for "Invalid" Variables

• To: mathgroup at smc.vnet.net
• Subject: [mg27716] RE: [mg27569] Solving for "Invalid" Variables
• From: "Higinio Ramos" <higra at gugu.usal.es>
• Date: Tue, 13 Mar 2001 03:52:36 -0500 (EST)
• Organization: usal
• References: <200103070908.EAA05042@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

----- Original Message ----- 
From: Alan <kd7cyb at mac.com>
To: mathgroup at smc.vnet.net
Subject: [mg27716] [mg27569] Solving for "Invalid" Variables


> Is there a way in Mathematica to solve for "invalid" variables? Example:
> 
> Solve[dy+y==dx+x, dy/dx]
> 
> This returns a invalid variable error but I want the result to say dy/dx
> is equal to something. Is there a way to do this with rules or anything
> else I may not know of?
> 
> Thanks,
> Alan
Perhaps this made what you want:
Solve[Map[Apart, Map[#/dx &, dy + y == dx + x, 1], 1] /. dy/dx -> var, 
    var] /. var -> dy/dx

Higinio

• References:
  • Solving for "Invalid" Variables
    • From: Alan <kd7cyb@mac.com>