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Re: Integration - another Integer as a result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93784] Re: [mg93743] Integration - another Integer as a result
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 25 Nov 2008 07:20:50 -0500 (EST)
  • Reply-to: hanlonr at cox.net

This integral evaluates on versions 5.2, 6.0.3, and 7 under Mac OS

Integrate[2 x Sin[n Pi x / l] Sin[k Pi x / l], x]

(l*((l*Cos[((k - n)*Pi*x)/l] + 
              (k - n)*Pi*x*Sin[((k - n)*Pi*x)/l])/
           (k - n)^2 - 
         (l*Cos[((k + n)*Pi*x)/l] + 
              (k + n)*Pi*x*Sin[((k + n)*Pi*x)/l])/
           (k + n)^2))/Pi^2

$Version

7.0 for Mac OS X x86 (64-bit) (November 11, 2008)

Integrate[2 x Sin[n Pi x / l] Sin[k Pi x / l], x]

(l*((Pi*x*(k - n)*Sin[
                  (Pi*x*(k - n))/l] + 
              l*Cos[(Pi*x*(k - n))/l])/
           (k - n)^2 - 
         (Pi*x*(k + n)*Sin[
                  (Pi*x*(k + n))/l] + 
              l*Cos[(Pi*x*(k + n))/l])/
           (k + n)^2))/Pi^2


Bob Hanlon

---- MikeSw <sowasowa at o2.pl> wrote: 

=============
Hello,

I'm trying to calculate an integer using Mathematica, but instead of getting a "normal" result I get another Integer. The algorithm available on Wolfram website does this calculation with no problem:

http://img156.imageshack.us/my.php?image=cakaqt6.jpg

but Mathematica gives this:

http://img156.imageshack.us/my.php?image=cakamtkmvk9.jpg

I guess there is something wrong with the input?


--

Bob Hanlon



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