Re: question (for Mathematica 6!)

*To*: mathgroup at smc.vnet.net*Subject*: [mg75581] Re: question (for Mathematica 6!)*From*: dimitris <dimmechan at yahoo.com>*Date*: Sat, 5 May 2007 06:12:11 -0400 (EDT)*References*: <f1ept5$4n1$1@smc.vnet.net>

Yes I know these. I just wonder why until now (5.2) we had for example Integrate[DiracDelta[x], x] D[%, x] UnitStep[x] DiracDelta[x] and now this has changed. Anyway...thanks for you response. Dimitris "Owen, HL (Hywel)" <h.l.owen at dl.ac.uk> wrote: HeavisideTheta[0] is undefined UnitStep[0] gives 1 Their integrals are the same (for example from -1 to 1). And: D[HeavisideTheta[x], x] is DiracDelta[x] Whereas D[UnitStep[x], x] is (-1 - DiscreteDelta[x] + UnitStep[-x] + UnitStep[x])/(1 - DiscreteDelta[x]) Hywel =CF/=C7 dimitris =DD=E3=F1=E1=F8=E5: > I don't have a copy of Mathematica 6 but having spent much time > reading the online documentation (not only because of curiosity!) I > have one question... > > Can somebody explain me the introduction of the HeavisideTheta > function > > http://reference.wolfram.com/mathematica/ref/HeavisideTheta.html > > in version 6? > > Note that the UnitStep function is still here > > http://reference.wolfram.com/mathematica/ref/UnitStep.html > > Dimitris