Re: Abs function
- To: mathgroup at smc.vnet.net
- Subject: [mg47281] Re: Abs function
- From: bobhanlon at aol.com (Bob Hanlon)
- Date: Fri, 2 Apr 2004 03:30:28 -0500 (EST)
- References: <c4ge4p$5a$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
It means that it does not know the derivative of Abs. You need to express Abs
in terms of a function for which it knows the derivative.
D[x(2UnitStep[x]-1), x]
2*x*DiracDelta[x] + 2*UnitStep[x] - 1
Simplify[%, #]& /@ {x<0, x>=0}
{-1, 1}
D[If[x<0, -x, x], x]
If[x < 0, -1, 1]
Bob Hanlon
In article <c4ge4p$5a$1 at smc.vnet.net>, nikmatz <nikmatz at math.ntua.gr> wrote:
<< i try to find the derivative of abs function
D[Abs[x],x]
and Mathematica answer
Abs`[x]
what mean that