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Re: evaluating functions and displaying results numerically

  • To: mathgroup at smc.vnet.net
  • Subject: [mg126187] Re: evaluating functions and displaying results numerically
  • From: prof.eduardofontana at gmail.com
  • Date: Tue, 24 Apr 2012 05:31:31 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201204210433.AAA29272@smc.vnet.net> <jn0l72$4th$1@smc.vnet.net>

thanks for the replies. I can go along with all your explanations for the Sin function, even though I havent had this interpretation of results from Mathematica before. I never had to use the N option before. What about my second enquire, reproduced below:
In another instance, I have a summation of about 1000 terms defined as
a function of 3 arguments. When I use numerical arguments to calculate the summation, instead of
Mathematica calculating a numerical result it generates a symbolic
output with all 1000 terms.
It doesnt make sense that Mathematica chooses to do the whole thing symbolically. I have made similar calculations before, and Mathematica performed the calculation numerically. I presume that I have enabled some sort of symbolic calculation mode, but I cannot figure out where. I am attaching a a link to a pdf file showing a image of the generated result for my function called "Absorption". The other functions called by Absorption are defined prior to the definition of Absorption. I just want to show the type of result generated. Also, If I want to plot my function Absorption relative to one of the arguments, Mathematica just doesnt plot it.
Best regards
The output image is in the google docs file below
https://docs.google.com/open?id=0Bw08G8QtolpXUDBnQUswdXUyVE0

Em domingo, 22 de abril de 2012 07h06min26s UTC-3, Murray Eisenberg  escreveu:
> Correct, the result of Sin[1] is _exactly_ Sin[1], whereas Sin[1.] will
> give you a decimal result that approximates the exact value.
>
> This is one of the most basic ideas of Mathematica -- that it can deal
> with exact symbolic quantities, like Pi or E or Sqrt[2] or Sin[1].
>
> Perhaps you need to read some of the introductory tutorials provided
> with Mathematica.
>
> On 4/21/12 12:33 AM, Eduardo Fontana wrote:
> > Once in a while a face a problem with Mathematica in which I cannot
> > get a straightforward numerical output.
> > I have a function defined in mathematica, I try to evaluate the
> > function with numerical arguments and mathematica returns a replica of
> > my function with the same arguments. It must be something I set
> > without noticing. I cannot get numerical results at all.
> > In another instance, I have a summation of about 1000 terms defined as
> > a function of 3 arguments. When I use numerical arguments, instead of
> > Mathematica calculating a numerical result it generates a symbolic
> > output with all 1000 terms. Even if a try something very simple such
> > as
> > In[1]: Sin[1]
> > the output is
> > Out[1]: Sin[1]
> > Could anyone give me a clue on this?
> > regards
> >
>
> --
> 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




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