Re: Mathematica cannot simplify a product of UnitStep functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg55136] Re: [mg55118] Mathematica cannot simplify a product of UnitStep functions*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 14 Mar 2005 03:43:36 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

Works fine in v5.1.1 $Version 5.1 for Mac OS X (January 27, 2005) e1=UnitStep[x-y];e2=UnitStep[x-z]; Simplify[{e1,e2,e1*e2},x<y<z] {0,0,0} FullSimplify[{e1,e2,e1*e2},x<y<z] {0,0,0} FunctionExpand[{e1,e2,e1*e2},x<y<z] {0,0,0} Bob Hanlon > > From: Alain Cochard <alain at geophysik.uni-muenchen.de> To: mathgroup at smc.vnet.net > Date: 2005/03/13 Sun AM 04:57:37 EST > To: mathgroup at smc.vnet.net > Subject: [mg55136] [mg55118] Mathematica cannot simplify a product of UnitStep functions > > Consider the following: > > Mathematica 4.0 for Linux > Copyright 1988-1999 Wolfram Research, Inc. > -- Motif graphics initialized -- > > In[1]:= e1=UnitStep[x-y]; e2=UnitStep[x-z]; > > In[2]:= FullSimplify[{e1,e2,e1*e2},x<y<z] > > Out[2]= {0, 0, UnitStep[x - y, x - z]} > > I find it strange that it cannot simplify the product to 0. Is there > something mathematically profound here, implying that the true result > is indeed not 0?? (At least I hope it's not something trivial!) > Assuming the answer is no, is there a smarter/more elegant way to > perform the simplification than the workaround I found, which is to > simplify each term and multiply them. > > Thanks in advance. > AC > > >