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MathGroup Archive 2006

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Re: On Reduce

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72020] Re: [mg72011] On Reduce
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 9 Dec 2006 06:09:26 -0500 (EST)
  • Reply-to: hanlonr at cox.net

BInv={{1/4, 1/4, 0},
      {-1/2, 1/2, 0},
      {3/4, -5/4, 1}};
B=Inverse[BInv];
b={4 + \[Delta], 8, 10};
BInv.b // Simplify;
ineq=Reduce[Thread[% >= 0], \[Delta]]/.
      {\[Delta] -> b1-4} // Simplify

0 <= b1 <= 8

{First@ineq, Last@ineq}

{0,8}

Cases[ineq, _?NumericQ]

{0,8}


Bob Hanlon

---- Virgil Stokes <vs at it.uu.se> wrote: 
> I have the following small piece of Mathematica code that works fine for 
> my purposes.
> 
>  BInv = {{  1/4, 1/4, 0},
>               {-1/2, 1/2, 0},
>               {  3/4, -5/4, 1}}
>  B = Inverse[BInv]
>  b = {4 + \[Delta], 8, 10};
>  BInv.b // FullSimplify
>  Reduce[{%[[1]] >= 0, %[[2]] >= 0, %[[3]] >= 0}, {\[Delta]}]
>  % /. {\[Delta] -> b1 - 4} // FullSimplify
> 
> which gives
> 
> 0 <=  b1 <= 8
> 
> which is of course correct. But, how can I use (access) the values 0 and 8?
> That is, I would like to now use these values in some expressions that 
> would follow this.
> 
> Thanks,
> V. Stokes
> 


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