Few MMA questions - need some help!

*To*: mathgroup at christensen.cybernetics.net*Subject*: [mg1001] Few MMA questions - need some help!*From*: pikus at dolphin.physics.ucsb.edu (Fedor G. Pikus)*Date*: Mon, 8 May 1995 04:38:26 -0400*Organization*: University of California, Santa Barbara

Hi, I need some help to make MMA do the calculation I want to: 1. MMA 2.2 cannot take the following integral: Integrate[E^(s t) E^(I wmk t),{t,-Infinity,T}] even if I write Integrate[E^(s^2 t) E^(I wmk t),{t,-Infinity,T}] which defines that at -Infinity Exp goes to 0, it still cannot take it. MMA 2.0 did take this integral, and the one before, where it assumed positive s. The integral with finite limits Integrate[E^(s^2 t) E^(I wmk t),{t,-A,T}] can be computed, but the limit cannot. What it so difficult about limit of E^(s^2 t) at t-> -Infinity? 2. I need to make MMA compute the integrals like this: Int[t Sum[f[k],{k,Infinity}],{t,0,1}] and Int[If[m == n, t, t^2], {t,0,1}] to Sum[f[k],{k,Infinity}] and If[m == n, 1, 1/2] respectively. I'd appreciate any help. Fedor Pikus