Re: Integer Assumptions in Integrations

• To: mathgroup at smc.vnet.net
• Subject: [mg20189] Re: Integer Assumptions in Integrations
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 5 Oct 1999 04:04:19 -0400
• Organization: Universitaet Leipzig
• References: <7t4ctm\$82s@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

your 'a' does not matter the result of the integration

Mathematica 4.0 return :

In[25]:=
Integrate[t^(a - 1)*Exp[-t], {t, q, Infinity}]

Out[25]=
Gamma[a, q]

and Mathematica 3.0.1

Integrate[t^(a-1)*Exp[-t], {t, q, Infinity},Assumptions->{q>0}]

Gamma[a, q]

In Mathematica 4.0 you can still using Simplify[_,Element[a,Integers]],
FullSimplify[_,Element[a,Integers]].

Hope that helps

Jens

Will Cooper wrote:
>
> Hello,
> How can I set a variable assumption to be an integer in an integration
> calculation?
>
> e.g. The incomplete gamma function is defined as Gamma[a,q] =
> Integrate[t^(a-1)*Exp[-t], {t, q, Infinity}]
>
> I want to set the assumption that 'a' is always an Integer.
>
> I don't want to round 'a' to the next lowest integer, i.e.
> Integrate[t^(Integer[a]-1)*Exp[-t], {t, q, Infinity}]
>
> I just want to indicate that 'a' only assumes integer values.
>
> Thanks for any assistance.
>
> Will Cooper.

```

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