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MathGroup Archive 2000

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Re: Thx for your help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23748] Re: [mg23712] Thx for your help
  • From: Jack Goldberg <jackgold at math.lsa.umich.edu>
  • Date: Mon, 5 Jun 2000 01:09:42 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Write Abs[x] in terms of UnitStep[x]:

        Abs[x] = 2x UnitStep[x]-x

If you cannot do this replacement "by hand" you will need to
Unprotect[Abs] first and write the above equation using

Abs[x_] := 2x*UnitStep[x]-x

The same observations hold for Sign[x].

Sign[x_] := 2 UnitStep[x] - 1

Jack




On Mon, 29 May 2000, [iso-8859-1] Jos\151[iso-8859-1]  [iso-8859-1] Mar\155a Lasso wrote:

> Hi,
> Thx for the answers to my last post, but I have a new question, similar to
> the last one, when I try: Integrate[Abs[x],x], there is no result, just the
> original input, what I am doing wrong?, I need some advice about a good
> book about Mathematica for beginers.Thx again.Best regards
>
> Jose M Lasso
>
>
>




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