Re: UnitStep

*To*: mathgroup at smc.vnet.net*Subject*: [mg52355] Re: [mg52326] UnitStep*From*: yehuda ben-shimol <benshimo at bgu.ac.il>*Date*: Wed, 24 Nov 2004 02:32:27 -0500 (EST)*References*: <200411230712.CAA29371@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Quotation from the help for UnitStep[] UnitStep[x] represents the unit step function, equal to 0 for x<0 and 1 for x\[GreaterEqual]0. When using the rule p->0 for 1/p UnitStep[1-p] you get 1/0 UnitStep[-1]. Mathematica tries to evaluate 1/0 first and this causes the error message If you try UnitStep[p-1] /p /.p->0 you will get Indeterminate which results from evaluating 0/0. You may try Limit[1/p UnitStep[p-1],p->0] and get 0 Which gives you the Limit but not the Value of UnitStep[p-1]/p I hope this helps yehuda Blimbaum, Jerry AA R22 wrote: >Why does the following give me 'indeterminate, infinite expression >encountered', etc. instead of zero.... > > >(1/p) UnitStep[p-1] /.p->0 > > >I defined a function using the UnitStep because p could = 0 and I >thought this would be the way around that problem.......but didnt work >the way I expected..... > > >jerry blimbaum > > > >

**References**:**UnitStep***From:*"Blimbaum, Jerry AA R22" <jerry.blimbaum@navy.mil>