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MathGroup Archive 1996

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Re: Integration..Constants

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5139] Re: [mg5119] Integration..Constants
  • From: Sherman Reed <Sherman.Reed at worldnet.att.net>
  • Date: Wed, 6 Nov 1996 01:33:00 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

At 03:04 AM 10/31/96 +0000, you wrote:
>I have tried several times to perform an integration(math..2.2.3)B 
>similar to the following.
>
>In[1]:=Integrate[(ao+x)^-1 (bo^-2), x]
>
>The results, however, are always incorrect:
>
>Out[1]=-ln(-ao+x)  <---where the constant "ao" should be positive.
>
>Note: The above is not the exact problem and solution. It is only an 
>example of the type of problem I have been having with the program.
>
>I have tried to specify the value of "ao" before integrating:
>
>In[1]:=SetAttribute[ao, Constant]
>
>or
>
>In[1]:=SetAttribute[ao, Protected]
>
>or a combination of the two.
>
>I have also tried:
>
>In[1]:=ao/. Sign[ao]=1
>
>To try and get a positive result.  I have also tried MathCad 6.0+ and 
>gotten the same results.  It appears to be a problem for both programs.  
>(For those that might think that I am the one with the problem, I would 
>like to say that a tenured prof and a postdoc agreed that there is a 
>problem with the program).  If you know of a solution, or can point me in 
>a different direction, I would greatly appreciate it.  This would save me 
>from having to contact Wolfram about his program.  
>
>
>-- 
>----------------------------------  -Dennis M. Winters               -
>-P.O. BOX 21215                  -
>-EMORY UNIVERSITY                -
>-ATLANTA, GA 30322               -
>-dwint01 at emory.edu               -
>-or winters at euch6h.chem.emory.edu-
>----------------------------------

Dennis,

I have 2.2.2 on a notebook and I get the correct result, specifically

In[3]:=Integrate[(ao+x)^-1*(bo^-2),x]
Out[3]=(Log[ao + x]\/bo\^2\)
In[4]:=Integrate[(ao+x)^-1,x]
Out[4]=Log[ao+x]

I have 3.0 on a Pent 166, Win 95, and I get the exact same result.

I also have 2.2.1 on a NeXT which gets the same result.

I would be glad to look at your problem, if you care to share it in more
detail.  I am more impressed with results than either postdocs or tenured
faculty. I taught Numerical Methods using Mma for 5 years at UTA.

Sherman C. Reed
Sr. Lecturer, University of Texas at Arlington (Retired)
AT&T-Bell Laboratories (Retired) 



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