Re: Simplify[Abs[x],x<0]]
- To: mathgroup at smc.vnet.net
- Subject: [mg39327] Re: [mg39303] Simplify[Abs[x],x<0]]
- From: Tomas Garza <tgarza01 at prodigy.net.mx>
- Date: Tue, 11 Feb 2003 04:42:34 -0500 (EST)
- References: <200302100607.BAA23841@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I do not wish to appear flippant, but if you wish to calculate Abs[x] and you know that x < 0, then evaluate Abs[-x] with the assumption that x >0: Abs[x] given that x <0 is equal to Abs[-x] given x > 0. In[1]:= Simplify[Abs[-x], x > 0] Out[1]= x Or else, use In[2]:= Simplify[ComplexExpand[Abs[x]], x < 0] Out[47]= -x to make sure you are talking of real x (I presume). Tomas Garza Mexico City ----- Original Message ----- From: "Uri Zwick" <zwick at cs.tau.ac.il> To: mathgroup at smc.vnet.net Subject: [mg39327] [mg39303] Simplify[Abs[x],x<0]] > Hi, > > Simplify[ Abs[x] , x>0 ] returns x. > But, Simplify[ Abs[x] , x<0] returns Abs[x], and not -x. > > Why is that? > > Uri > > >
- References:
- Simplify[Abs[x],x<0]]
- From: Uri Zwick <zwick@cs.tau.ac.il>
- Simplify[Abs[x],x<0]]