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Re: Multiple Constants

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83240] Re: Multiple Constants
  • From: Szabolcs Horvát <szhorvat at gmail.com>
  • Date: Fri, 16 Nov 2007 05:19:37 -0500 (EST)
  • References: <fhh80l$946$1@smc.vnet.net>

thehammerster at gmail.com wrote:
> Hi,
> I'm new to Mathematica and I feel like this is a stupid question but I
> can't seem to define more than one constant
> 
> If I type
> SetAttributes[a,b,c,Contstant]
> I get
> SetAttributes::argrx: SetAttributes called with 4 arguments; 2
> arguments are \expected.
> 
> I have three equations and three variables I want to solve for and I
> have 8 constants.
> 
> x+y+z=1
> b*x+c*y+d*z=A
> f*x+g*y+h*z=Q
> 
> b,c,d,A,f,g,h,Q are constants and I want a generic equations that I
> can use for many different variations of these constants.
> 
> I've done the calculation by hand but fear I have made a mistake and
> would like to double check my calculation, and then use the equation
> to propagate my errors, as each constant has an associated standard
> error of the mean. Propagation of my error will give me an error on my
> model calculation, which is really important.
> 
> Thanks
> 

SetAttributes[{a, b, c}, Constant],

but you do *not* need to do this unless you wish to calculate total 
derivatives using Dt[].

Just use
Solve[{x + y + z == 1, b*x + c*y + d*z == A, f*x + g*y + h*z == Q},
    {x, y, z}]

-- 
Szabolcs


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