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Defining a constant in Mathematica

by ToxicBug
Tags: constant, defining, mathematica
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ToxicBug
#1
Mar24-09, 02:08 AM
P: 85
Hello, I've been breaking my head over this for a couple hours now.

I'm trying to find the expected value of a Gumbel distribution.
Integrate[ y*E^(-((y - a)/b))*E^(-E^(-((y - a)/b)))/b, {y, -Infinity, Infinity},
  Assumptions -> b > 0]
If I set a = 2 and b = 5, it works. Otherwise it gives me a very complicated expression. I've tried SetAttributes[a, Constant], but it doesn't do the trick. Anyone know how can I solve this?
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CompuChip
#2
Mar24-09, 03:46 AM
Sci Advisor
HW Helper
P: 4,300
Try giving it some information about a, like
Assumptions -> b > 0 && Element[a, Reals]


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