MathGroup Archive 1992

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  • From: heinz at (Schulz)
  • Date: Mon, 26 Oct 92 10:47:50 +0100

an apparently trivial problem:

(i) mma knows
      Integrate[x^n  E^(-x), x] = -Gamma[1 + n, x]
    which is pretty good of it (for non-integer n, most people would have to look this up in
a book).

(ii) BUT: 

In[4]:= Integrate[x^n  E^(-a x), x]

Out[4]= Integrate[----, x]
                   a x
now, that looks pretty dumb to me, given that mma already knows the essential result
(i). There are scores of other similar examples, involving different functions, which
can be easily produced. What would be the (general, if possible) solution to this?

H.J. Schulz,
Laboratoire de Physique des Solides,
Universite Paris-Sud, Orsay, France

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