Re: Limit[ Sign[],x->Infinity ]
- To: mathgroup at smc.vnet.net
- Subject: [mg27286] [mg27286] Re: [mg27289] Limit[ Sign[],x->Infinity ]
- From: BobHanlon at aol.com
- Date: Sun, 18 Feb 2001 02:52:18 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Why would you take the limit rather than just indicate that x is positive? Simplify[Sign[x]*Sign[z], x > 0] Sign[z] Simplify[Sign[x]+Sign[z], x > 0] Sign[z] + 1 Bob Hanlon In a message dated 2001/2/16 4:27:39 AM, jackgold at math.lsa.umich.edu writes: >I give you two examples using ver. 4.0 on a Mac and a unix system. > > Limit[ Sign[x]*Sign[z],x->Infinity ] > >yields Sign[z] which is good. > > Limit[ Sign[x]+Sign[z],x->Infinity] > >yields an expression too ugly to present to a wide audience, which is bad. > >Its not a bug since > > Limit[ Sign[x]+Sign[z],x->Infinity]//FullSimplify > >yields 1+Sign[z] which is good. > >I propose the name "buglet" to describe such "features" :-). By the way, >I tried some obvious variations on combinations of Sign[z] and Sign[x] >and >found it pretty hard to predict the output. >