Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

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

Search the Archive

Re: Modulus / Absolute Value

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90080] Re: [mg90058] Modulus / Absolute Value
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 28 Jun 2008 05:52:15 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200806271019.GAA24305@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

What problem are you actually trying to solve?  (You do not say!)

Why are you using awkward LaTeX mark-up here?  (Since you have a 
Mathematica question, why not start with Mathematica notation?  Type it 
into a Mathematica notebook, then use Edit > Copy As > Plain Text to 
copy it into your e-mail message.)

What does the function g have to do with this?  (I don't see its 
relevance at all; I think your question is really about integrating f, 
isn't it?)

Possibly the question you are asking is, in effect, how to find the 
total area enclosed between the graph of

   f[x_] := Sin[2x]

and the x-axis over the interval from 0 to Pi.  This is simply:

   Integrate[ Abs[f[x]], {x, 0, Pi} ]

Perhaps you wanted to add to that the area enclosed by the graph of g 
and the x-axis, over that same interval.  You could add to the preceding 
the value of

   Integrate[ Abs[g[x]], {x, 0, Pi} ]

or, since g[x]<= 0 when 0 <=x <= Pi, simply add

   - Integrate[g[x], {x, 0, Pi} ]

Felipe Mannshardt wrote:
> Greetings,
> 
> i have been searching the way to tell Mathematica to use Modulus / Absolute Value.  I have been unable to find.
> 
> LATEX
> \left(\int_0^{\frac{\pi }{2}} f[x] \, dx+\int_{\frac{\pi }{2}}^{\pi } f[x] \, dx\right)+\int_0^{\pi } g[x] \, dx
> /LATEX
> I should be subtracting the upper Integral from the lower Integral,
> but since i could not find a way to tell Mathematica to use Modulus /Absolute Value.  I had to add the upper to the lower . . .
> 
> my functions are, f and g
> 
> LATEX
> f[\text{x$\_$}]\text{:=}\text{Sin}[2*x]g[\text{x$\_$}]\text{:=}x^2-(\pi *x)
> /LATEX
> So, can some1 help me out with this one? How to use Modulus/Absolute Value (German, Betrag) with Mathematica.
> 
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


  • Prev by Date: Re: Re: Problem with NMaximize
  • Next by Date: Re: Reading a module library from plain text file
  • Previous by thread: Modulus / Absolute Value
  • Next by thread: Re: Modulus / Absolute Value