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? >> > > >

**References**:**Using Coefficient on an equation***From:*carlos@colorado.edu