MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Limit[ Sign[],x->Infinity ]

  • To: mathgroup at
  • Subject: [mg27286] Re: [mg27289] Limit[ Sign[],x->Infinity ]
  • From: BobHanlon at
  • Date: Sat, 17 Feb 2001 03:31:04 -0500 (EST)
  • Sender: owner-wri-mathgroup at

Why would you take the limit rather than just indicate that x is positive?

Simplify[Sign[x]*Sign[z], x > 0]


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 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]
>found it pretty hard to predict the output. 

  • Prev by Date: Re: String to Number
  • Next by Date: Re: two y-axis
  • Previous by thread: Limit[ Sign[],x->Infinity ]
  • Next by thread: Re: Limit[ Sign[],x->Infinity ]