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Re: evaluating functions and displaying results numerically

  • To: mathgroup at smc.vnet.net
  • Subject: [mg126169] Re: evaluating functions and displaying results numerically
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sun, 22 Apr 2012 06:08:04 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

On 4/21/12 at 12:33 AM, prof.eduardofontana at gmail.com (Eduardo
=46ontana) 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


By default, Mathematica gives an exact answer whenever you
supply exact values. Since Sin[1] is not a rational value,
Mathematica returns the result as Sin[1] which is an exact answer.

If you want a numerical approximation to Sin[1] there are two
choices. First, would be to input Sin[1.] instead of Sin[1], i.e.,

In[1]:= Sin[1.]

Out[1]= 0.841471

This works since Mathemtica by default returns an approximate
number whenever you provide approximate numbers as inputs. The
value 1. is an approximate number.

The other way would be to use N to convert the result to an
approximate number, i.e.,

In[2]:= Sin[1] // N

Out[2]= 0.841471




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