Re: Integration by substitution

*To*: mathgroup at smc.vnet.net*Subject*: [mg29824] Re: [mg29800] Integration by substitution*From*: "J Rockmann" <mtheory at msn.com>*Date*: Thu, 12 Jul 2001 02:52:37 -0400 (EDT)*References*: <200107110025.UAA20901@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

----- Original Message ----- From: "G. A. Garrett" <ggarrett7 at netscape.net> To: mathgroup at smc.vnet.net Subject: [mg29824] [mg29800] Integration by substitution > 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-- > If I'm not mistaken, Mathematica will consider "sp" as a single variable as it would "x". Therefore, the two statements are not equivalent to Mathematica after any algebraic manipulation has been performed on your naming of the variable "sp=sa". I hope this helps, Jonathan Rockmann mtheory at msn.com

**References**:**Integration by substitution***From:*ggarrett7@netscape.net (G. A. Garrett)