Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2003
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2003

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

Search the Archive

Re: Domain of Sin[ArcSin[x]] ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39639] Re: [mg39620] Domain of Sin[ArcSin[x]] ?
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 27 Feb 2003 00:27:34 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

What would you like to happen when ArcSin[x] is not a real number? If 
you are happy with the usual error messages ("not a machine size real 
...") then you can do something like this:

define

IsReal[x_] := If[Element[x, Reals], x]

and evaluate

Plot[Sin[IsReal[ArcSin[x]]], {x, -3, 3}]



Andrzej Kozlowski
Yokohama, Japan
http://www.mimuw.edu.pl/~akoz/
http://platon.c.u-tokyo.ac.jp/andrzej/




On Wednesday, February 26, 2003, at 04:42  pm, Michael Buescher wrote:

> I want to demonstrate to my students that in the real number system,
> Sin[ArcSin[x]] is only defined on [-1,1] because that is the domain of
> ArcSin[x].  When I Plot the composition, however, I get Sin[ArcSin[x]] 
> =
> x for all real numbers, not just on [-1,1].  I tried this both with and
> without the RealOnly package.
>
> Is there any way to ensure that Mathematica uses only real numbers in
> its calculations, so that Sin[ArcSin[x]] is undefined when ArcSin[x] is
> not a real number?
>
> Michael Buescher
> Hathaway Brown School
>
>
>
>



  • Prev by Date: Re: Why Plot cannot run under package?
  • Next by Date: Re: signal detector question
  • Previous by thread: Re: Domain of Sin[ArcSin[x]] ?
  • Next by thread: RE: Domain of Sin[ArcSin[x]] ?