Re: Re: Reduce/Solve
- To: mathgroup at smc.vnet.net
- Subject: [mg49995] Re: [mg49990] Re: Reduce/Solve
- From: DrBob <drbob at bigfoot.com>
- Date: Tue, 10 Aug 2004 06:02:51 -0400 (EDT)
- References: <200408090829.EAA03580@smc.vnet.net>
- Reply-to: drbob at bigfoot.com
- Sender: owner-wri-mathgroup at wolfram.com
It's especially sad, coming on the heels of Andrsej's valiant DEFENSE of Reduce! Bobby On Mon, 9 Aug 2004 04:29:32 -0400 (EDT), Dana DeLouis <delouis at bellsouth.net> wrote: > Hello. It is because of Mathematica's huge bug in variable names. Reduce > often doesn't work because of this bug. The first thing you need to try is > to change the variable name. I would first start by changing the "r" to a > variable name that comes near the beginning of the alphabet, like "a" (at > least something before the "d" in the equation). > > Taking your equation, and changing r to a: > > eq = J == J0*(1 + r/d)*Exp[-(r/d)] /. r -> a > > J == ((1 + a/d)*J0)/E^(a/d) > > Now it should work: > > tt = Reduce[eq, a] > > d != 0 && J == 0 && > (J0 == 0 || a == -d) || > C[1] ? Integers && > J != 0 && J0 != 0 && > d != 0 && a == > -d - d*ProductLog[C[1], > -(J/(E*J0))] > > HTH > Sad, isn't it! > > Dana > > > "Dr A.H. Harker" <a.harker at ucl.ac.uk> wrote in message > news:cetf3i$6i8$1 at smc.vnet.net... >> Dear All, >> I tend to think of Reduce as a more powerful tool than Solve, >> yet with >> >> eq = J == J0 (1 + r/d) Exp[-r/d] >> ss = Solve[eq, r] >> tt = Reduce[eq, r] >> >> I get useful output from Solve, but Reduce returns the expression >> unevaluated. What am I missing? Mathematica 5.0.0.0 under Windows XP. >> >> Tony >> >> Dr A.H. Harker >> Director of Postgraduate Studies >> Deputy Head, Condensed Matter and Materials Physics Group >> Department of Physics and Astronomy >> University College London >> Gower Street >> LONDON >> WC1E 6BT >> (44)(0)207 679 3404 >> a.harker at ucl.ac.uk >> >> >> > > > -- DrBob at bigfoot.com www.eclecticdreams.net
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- Re: Reduce/Solve
- From: "Dana DeLouis" <delouis@bellsouth.net>
- Re: Reduce/Solve