Re: Re: Thx for your help
- To: mathgroup at smc.vnet.net
- Subject: [mg23787] Re: [mg23743] Re: Thx for your help
- From: Jack Goldberg <jackgold at math.lsa.umich.edu>
- Date: Sat, 10 Jun 2000 02:59:34 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Hi, Replace Abs[x] by 2x UnitStep[x]-x. Mathematica knows the integral of x*UnitStep[x] and gets the correct answer in form of a UnitStep, -x^2/2+x^2*UnitStep[x] which, if you factor the x^2/2 yields the answer below. jack On Mon, 5 Jun 2000, Jens-Peer Kuska wrote: > Hi, since Mathematica don't know that > > x^n*DiracDelta[x]== 0 /; n>0 > > it can't find that Integrate[Abs[x],x]-> x^2*Sign[x]/2 > > As book advice *not* a Mathematica book, a mathematics book > seems to be more use full. > > Regards > Jens > > Jos\151 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 > >