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MathGroup Archive 2004

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Re: seruous solve bug? only when used with simplifying

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48693] Re: [mg48634] seruous solve bug? only when used with simplifying
  • From: sean kim <sean_incali at yahoo.com>
  • Date: Thu, 10 Jun 2004 02:44:35 -0400 (EDT)
  • Reply-to: sean_incali01 at yahoo.com
  • Sender: owner-wri-mathgroup at wolfram.com

ok. 

now I see where I made a mistake from your comments
and other's... 

I Didn't mean to insinuate that a function you made
had bugs. It just seemed at the time to be incorrect.

Solve came before simplify and fullsimplify. I didn';t
include it because it was kinda long routine. 

sorry everyone. 


sean 

(i'm too scared to ask about Solve[] function now.
kidding. lol)



--- Daniel Lichtblau <danl at wolfram.com> wrote:
> sean kim wrote:
> > hello group, 
> > 
> > i think i have a serious Solve[], Simplify[],
> FullSimplify[] bug...
> > 
> > 
> > Take a system of equations as below. (apb is
> actually (a+b). i defined
> > it as apb to keep Mathematica crunching away at
> it)
> > 
> > sys = 
> > {c1[t] == (c*(16*a^4 + 8*a^3*kd + 4*a^2*apb*kd +
> 2*a*apb^2*kd +
> > apb^3*kd))/(apb^4*kd),
> > c2[t] == (2*(8*a^3 + 4*a^2*apb + 2*a*apb^2 +
> apb^3)*b*c)/(apb^4*d), 
> > c3[t] == (2*(8*a^3 + 4*a^2*apb + 2*a*apb^2 +
> apb^3)*b*c)/(apb^4*kd)}
> > 
> > sys1 = sys /.{apb -> (a + b)}
> > sys2 = sys/.{apb -> (a + b)}//Simplify
> > sys3 = sys/.{apb -> (a + b)}//FullSimplify
> > 
> > and then use
> > 
> > TrueQ[sys1 == sys1]
> > TrueQ[sys1 == sys2]
> > TrueQ[sys1 == sys3]
> > TrueQ[sys2 == sys3]
> > 
> > then it gives, 
> > 
> > Out[18]=True
> > Out[19]=False
> > Out[20]=False
> > Out[21]=False
> > 
> > Simplify and FullSimplify changed the system so
> much that they are not
> > equal?
> > 
> > Basically, unless I define the (a+b) as a single
> constant apb, the Mathematica
> > will do soemthing with it then it messes it up. I
> think...
> > 
> > Why is this happening? and how do i prevent it
> from happening again
> > with other more obsucre systems?  Above I got
> lucky in finding the
> > cause (a+b)
> > 
> > thanks in advance for any and all comments. 
> > 
> > Sean
> Umm, where did you use Solve? What would make you
> think you have 
> anything other than a serious lack of understanding
> of the semantics of 
> Mathematica's Equal? Why did you not check section
> 1.5.5 of The 
> Mathematica Book, accessible through a link from
> Equal in the Help 
> Browser? Why would you formulate an utterly
> misleading subject header 
> for a note such as this?
> 
> 
> Daniel Lichtblau
> Wolfram Research
> 
> 



	
		
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