Simple integration that Mathematica can't do?
- To: mathgroup at smc.vnet.net
- Subject: [mg27641] Simple integration that Mathematica can't do?
- From: "A. E. Siegman" <siegman at stanford.edu>
- Date: Fri, 9 Mar 2001 02:35:55 -0500 (EST)
- Organization: Stanford University
- Sender: owner-wri-mathgroup at wolfram.com
I'm a little surprised that Mathematica can't do the following fairly simple calculation: f[x_] := Sqrt[4a^3] x Exp[-a x] u = Integrate[ f[x] f[x - 1], {x, 1, Infinity}, Assumptions -> {Re[a] > 0}] even though if I break it apart by hand into the form u1 = 4a^3 Exp[a] Integrate[x^2 Exp[-2a x], {x, 1, Infinity}, Assumptions -> {Re[a] > 0}] u2 = 4a^3 Exp[a] Integrate[x Exp[-2a x], {x, 1, Infinity}, Assumptions -> {Re[a] > 0}] u = u1 - u2 it can do both of the component integrals with no problem.