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Re: defining a integer greater than one

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  Re: defining a integer greater than one Bill Rowe <readnews@sbcglobal.net> - 2011-04-02 22:04 +0000

#1439 — Re: defining a integer greater than one

On 4/2/11 at 2:41 AM, karina.erlang@yahoo.de (Karina Erlang) wrote:

>I am new to Mathematica and cannot seem to achieve the following. I
>want to integrate an expression but Mathematica gives me a
>nonsensical if answer. (If Re(n)>1 then etc). How can I define n
>being greater than one before that integration. I can only achieve
>to make it an integer with the Element[] function.

You really need to post the details of what you are trying to do
with the Mathematica code to get answers that best apply to what
you are attempting. Meanwhile, look at the documentation for
Assuming. For example,

In[6]:= Assuming[ a > 0 && a s < 1,
  Integrate[Exp[s t] Exp[-t/a]/a, {t, 0, Infinity}]]

Out[6]= 1/(1 - a*s)

Contrast that with the result you get from

Integrate[Exp[s t] Exp[-t/a]/a, {t, 0, Infinity}]

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