Re: Why does Mathematica 5.0 fail where Mathematica 4.1 works ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg47022] Re: Why does Mathematica 5.0 fail where Mathematica 4.1 works ?*From*: drbob at bigfoot.com (Bobby R. Treat)*Date*: Sat, 20 Mar 2004 03:50:34 -0500 (EST)*References*: <c3e5b5$qm1$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

y isn't "an unknown variable," of course. YOU introduced the variable, and didn't tell Solve to eliminate it... so it didn't. (It can't, in this case, but that's another matter entirely.) You wanted y==E, so make the substitution y->E and you'll have the same answer as in version 4.1. Bobby Oleksandr Pavlyk <pavlyk at phys.psu.edu> wrote in message news:<c3e5b5$qm1$1 at smc.vnet.net>... > Hi, > > I was looking at excellent talk by Daniel Lichtblau > "Tactics for solving equations in Mathematica" from > > http://library.wolfram.com/infocenter/Conferences/337/ > > In the "Tricky Solve problem" chapter we find the > following > > k = E; > Solve[ { y == x^y , y == k }, x ] > > So here are outputs in the freshly started notebooks in > two versions of Mathematica > > Mathematica 4.1 on Solaris returns > > E^(1/E) > > and Mathematica 5.0 on Windows returns > > (1/y)^(-1/y) > > where y is an unknown variable. > > Both versions complain that inverse functions were used and hence > some solution maybe lost. See output from 5.0 attached below. > > I would not be surprised of somebody tells me this bug has been fixed > in 5.0.1. In fact this is what happened with all earlier bug reports > posted on this mailing list. > > I must ask our sysadmin if our departmental subscription > qualifies for a free upgrade to Mathematica 5.0.1. ;) > > I can't help but feel that Mathematica should provide bug > (not limitation) fixing patches for Mathematica users free > of charge. But that's me... > > Sasha > > In[1]:= > $Version > > Out[1]= > 5.0 for Microsoft Windows (June 11, 2003) > > In[2]:= > sol = x /. First[Solve[{y == x^y, y == E}, x]] > > From In[2]:= > \!\(\* > RowBox[{\(Solve::"ifun"\), \(\(:\)\(\ \)\), "\<\"Inverse functions are > being used by \\!\\( > Solve\\), so some solutions may not be found; use Reduce for > complete \ > solution information. \\!\\(\\*ButtonBox[\\\"More?\\\", \ > ButtonStyle->\\\"RefGuideLinkText\\\", ButtonFrame->None, \ > ButtonData:>\\\"Solve::ifun\\\"]\\)\"\>"}]\) > > Out[2]= > \!\(\((1\/y)\)\^\(\(-1\)/y\)\)