Re: Integration question
- To: mathgroup at smc.vnet.net
- Subject: [mg21110] Re: Integration question
- From: Harald Giese <giese at dkrz.de>
- Date: Fri, 17 Dec 1999 01:21:09 -0500 (EST)
- Organization: Institut fuer Meereskunde, Universitaet Hamburg
- References: <831ivc$dgf@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
V Stokes wrote:
>
> Please try the following simple tests:
>
> Integrate[Exp[x-a],x]
>
> then,
>
> Integrate[Exp[x-a],{x,-Infinity,a}]
>
> I get the following solution (with Mathematica 3.01)
>
> If[a<0,1,...]
>
> Is this the intended solution for this integral? A simple calculation
> shows that this integral will evaluate to 1 for any a > 0 !
>
Virgil,
you don't need Mathematica to do this calculation.
Any textbook on analysis should tell you that D[Exp[x-a]] -> Exp[x-a],
and, of course,
Integrate[Exp[x-a],x] -> Exp[x-a]
Integrate[Exp[x-a],{x,-Infinity,a}] -> (Exp[a-a] - Exp[-Infinity-a])
-> (Exp[0] - Exp[-Infinity])
-> (1 - 0)
-> 1
Regards,
Harald
--- This message was entirely written using recycled electrons ---
Harald Giese
Email: giese at dkrz.de
Phone: +49 (0)40 42838 5796; Fax: +49 (0)40 5605724
Institut fuer Meereskunde der Universitaet Hamburg
(Institute of Oceanography of the University of Hamburg)
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