Re: Mathematica cannot simplify a product of UnitStep functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg55141] Re: [mg55118] Mathematica cannot simplify a product of UnitStep functions*From*: "Christoph Lhotka" <lhotka at astro.univie.ac.at>*Date*: Mon, 14 Mar 2005 03:43:40 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, on version 5.1 it works... In[..]:=Simplify[{e1, e2, e1*e2}, x < y < z] Out[..]:= {0, 0, 0} with kind regards... On Sun, 13 Mar 2005 04:57:37 -0500 (EST) Alain Cochard <alain at geophysik.uni-muenchen.de> wrote: > 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 > > -- Christoph Lhotka -- University of Vienna Institute for Astronomy Tuerkenschanzstr. 17 1180 Vienna, Austria fon. +43.1.4277.518.41 mail. lhotka at astro.univie.ac.at