MathGroup Archive 1997

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  • To: mathgroup at
  • Subject: [mg8024] IntegerQ
  • From: "K. Nikolaj Berntsen" <knb at>
  • Date: Sat, 2 Aug 1997 22:32:34 -0400
  • Organization: News Server at UNI-C, Danish Computing Centre for Research and Education.
  • Sender: owner-wri-mathgroup at

If this is posted twice, please forgive me; I posted it yesterday and it
has not appeared yet, so I try by another channel.

I am looking for a way to tell mathematica that "n" is an integer AND to
use that piece of information.

I have tried something like

In[]=   n /: IntegerQ[n]=True
Out[]=  True

But this does not seem to get through to mathematica, other than when
you explicitely ask the question 
In[]= IntegerQ[n]

For example mathematica cannot do the following:
In[]=   Sin[n Pi] 
Out[]=  0

Of course I do not really care for the above identity, but I do want to
carry out an integration like

Integrate[Exp[Cos[x]] Cos[n x],{x,0,2 Pi}]

Mathematica can do this for any "n" I have come with, but it can not
me the general expression (well sometimes it can, in the beginning of a

Another example would be to get

Integrate[Cos[x]^n,{x,0,2 Pi}]

In the same form as (or whatever integer you choose to put in)

Integrate[Cos[x]^3,{x,0,2 Pi}]

Maybe it would be necessary to tell mathematica that it is an even or
odd number, but that does not seem to help it out:

In[]=    n/: EvenQ[n]=True
Out[]=   True
In[]=    Integrate[Cos[x]^n,{x,0,2 Pi}]

Anybody out there who has as way to do it?

| Ph.D. stud., cand.scient.                                  |
| K. Nikolaj Berntsen                                        |
| Office: Department of Structural Engineering and Materials |
|         Technical University of Denmark                    |
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|         DK-2800 Lyngby                                     |
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