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MathGroup Archive 2004

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RE: Simple Differentiation?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46023] RE: [mg46014] Simple Differentiation?
  • From: "sabrina casagrande" <sabrinacasagrande at hotmail.com>
  • Date: Tue, 3 Feb 2004 03:20:53 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

I'm not very confident with Math ematica. I'm learning now for College purpose...
Anyway, I think it's a little bug in your code. Let's explain... When you define
f[x_]+g[x_]^:=1, you are saying to mathematica that when it find f[x_]+g[x_], it must
replace it with 1. so the derivatives of a costant is zero. 
I think so. If I'm wrong, let me know.
ciao
sabbri

  From: "Sunil Pinnamaneni" <PINNAMA at CIMS.NYU.EDU>
To: mathgroup at smc.vnet.net
  To: mathgroup at smc.vnet.net
  Subject: [mg46023] [mg46014] Simple Differentiation? 
  Date: Mon, 2 Feb 2004 05:21:28 -0500 (EST) 
 
  In Mathematica 5.0, if one types in: 
 
  f[x_]+g[x_]^:=1 (1) 
 
  and then types 
 
  dx(f[x]+g[x]) 
 
  we get 0. 
 
  However, if we type dx(f[x]) + dx(g[x]) after typing (1), we get 
 
  f'[x] + g'[x]. 
 
  Mathematica doesn't recognize that f'[x]+g'[x]= 
  dx(f[x]+g[x]), which equals 0. How does one get Mathematica to do this? 
 
  I'm interested in more complicated examples, which involve more complex 
  differential relations, but I should be able to do things in those 
  situations given a nice, natural way of handling this toy case. Though this 
  seems like a pretty simple thing, I wasn't able to find any thing in the 
  Mathematica Book or elsewhere, which would help with this type of things. 
 
  Thanks, 
  Sunil 
 
 


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