Integration with non-numeric parameters - comp.soft-sys.math.mathematica

Message from discussion Integration with non-numeric parameters
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From: ingramfina...@gmail.com
Newsgroups: comp.soft-sys.math.mathematica
Subject: Integration with non-numeric parameters
Date: Fri, 3 Aug 2007 10:51:55 +0000 (UTC)
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When I use Mathematica to solve the following
y=x1/(2*sigma^2*t)

Integrate[y, {t, .5, 1}]

I get the following answer:

(0.34657*x1/sigma^2)

OK, so far, so good. It appears that I can generate an answer with a
non-numeric parameter. Note that I am looking for an answer in terms
of x1.

But when I try

 q=Exp[-(x1-t)^2/2*sigma^2*t]

Integrate[q, {t, .5,1}]

Now Mathematica does not solve this integral, it just repeats the
command



I am trying to get an expression in terms of x1. Why do I get a
statement like this instead of an answer?  There is something about
the functional form of the integrand that is causing the problem, I
just don't know what it is.


Any help you can give me is much appreciated!