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Re: Simplify UnitStep expressions
*To*: mathgroup at smc.vnet.net
*Subject*: [mg69205] Re: [mg69195] Simplify UnitStep expressions
*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>
*Date*: Fri, 1 Sep 2006 18:41:05 -0400 (EDT)
*References*: <200609011041.GAA25645@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
On 1 Sep 2006, at 11:41, L. Dwynn Lafleur wrote:
> The following is transcribed from a Mathematica 5.2 notebook in
> Windows XP:
>
> In[1]:= Simplify[UnitStep[a-x/b], a-x/b > 0]
> Out[1]= 1
>
> In[2]:= Simplify[UnitStep[a-Pi/b], a-Pi/b > 0]
> Out[2]= UnitStep[a-Pi/b]
>
> Why does the second output different from the first? I know it has
> something to do with the fact that Pi is internally defined in
> Mathematica
> because a similar result occurs Pi is replaced with E, but what
> logic is
> being followed?
>
> --
> ======================================
> L. Dwynn Lafleur
> Professor of Physics
> University of Louisiana at Lafayette
> lafleur at louisiana.edu
> ======================================
>
Curiously, if you use FullSimplify rather then Simplify you will get:
FullSimplify[UnitStep[a-Pi/b], a-Pi/b > 0]
1
The same holds if Pi is replaces by E, or indeed by explicit
functions of E or Pi such as Pi^2, E^Pi etc. In all such cases
FullSimplify works but Simplify does not work. Strange.
Andrzej Kozlowski
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