Integration by substitution

*To*: mathgroup at smc.vnet.net*Subject*: [mg29800] Integration by substitution*From*: ggarrett7 at netscape.net (G. A. Garrett)*Date*: Tue, 10 Jul 2001 20:25:36 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I was wondering if someone could explain to me why the first input below gives no answer while the second input does. It never crossed my mind the Mathematica wouldn't have seen the simple substitution of sp=s/a that produced an answer. I am running ver. 4.0 in a Windows environment. I am basically looking for a characteristic that I can be on the look out for in the future. Integrate[Sech[s/a]^2 Sech[(t - s)/a]^2, {s, -Infinity, Infinity}] Integrate[a Sech[sp]^2 Sech[(tp - sp)]^2, {sp, -Infinity, Infinity}] Gregory --Posted email rarely checked--

**Follow-Ups**:**Re: Integration by substitution***From:*"J Rockmann" <mtheory@msn.com>