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Re: Reduce::inex problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114350] Re: Reduce::inex problem
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 2 Dec 2010 05:37:01 -0500 (EST)

On 1 Dec 2010, at 08:13, Eduardo Cavazos wrote:

> Hello,
> 
> This seems like a pretty simple set of equations, but it's stumping
> reduce:
> 
> {
>  Subscript[V, b] == 4/3*Pi*Subscript[r, b]^3,
>  Subscript[V, a] == 4/3*Pi*Subscript[r, a]^3,
>  V == Subscript[V, b] - Subscript[V, a],
>  \[Rho] == m/V
>  };
> % /. {Subscript[r, b] -> 5.75,
>   Subscript[r, a] -> 5.70, \[Rho] -> 8.92};
> Reduce[%]
> 
> Of course, Solve can handle it. (Change the last expression to
> Solve[%,m].)
> 
> Any thoughts on helping Reduce out here?
> 
> Ed
> 

Clearly Reduce does not like subscripts. 
 {Vb == (4*Pi*rb^3)/3, Va == (4*Pi*ra^3)/3, 
  V == Vb - Va, \[Rho] == m/V}; 

% /. {rb -> 5.75, ra -> 5.7, \[Rho] -> 8.92}; 

 Reduce[%]

Vb == 796.3282878380627 && Va == 775.7346243950061 && 
   V == 20.593663443056585 && m == 8.92*V

Andrzej Kozlowski


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