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Re: Using Coefficient on an equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95515] Re: Using Coefficient on an equation
  • From: dh <dh at metrohm.com>
  • Date: Tue, 20 Jan 2009 05:49:30 -0500 (EST)
  • References: <200901181033.FAA13999@smc.vnet.net> <gl1bjo$93s$1@smc.vnet.net>


Hi,

the first example is wrong. "Coefficient" only works on polynomial or 

list of polynomials. It does not work on expressions with head "Equal".

Daniel



DrMajorBob wrote:

> f = a*x^2 + b*x + c == 0;

> First@Coefficient[f, x^2]

> 

> a

> 

> or

> 

> Coefficient[First@f, x^2]

> 

> a

> 

> Bobby

> 

> On Sun, 18 Jan 2009 04:33:11 -0600, <carlos at colorado.edu> wrote:

> 

>> If f=a*x^2+b*x+c, Coefficient[f,x^2] obviously returns a.

>> But if f=a*x^2+b*x+c==0, it returns 0.

>>

>> The problem arose using the Calculus`VariationalMethods` package.

>> It (unfortunately) returns the Euler-Lagrange equations as

>> such, so I have to remove the useless ==0 appendage for

>> Coefficient to work properly. Is there a simple direct way out?

>>

> 

> 

> 




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