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MathGroup Archive 2007

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Re: Indefinate integrals, erroneus Natural log?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77891] Re: [mg77842] Indefinate integrals, erroneus Natural log?
  • From: Curtis Osterhoudt <cfo at lanl.gov>
  • Date: Tue, 19 Jun 2007 06:37:39 -0400 (EDT)
  • Organization: LANL
  • References: <200706181055.GAA19440@smc.vnet.net>
  • Reply-to: cfo at lanl.gov

Hi, David, 

    The mistake is not putting an additional multiplication sign between 
the "x" and the "E" in the integrand. Once you do that, Mathematica will give 
you the expected---and correct---answer.



On Monday 18 June 2007 04:55:50 David Rees wrote:
> Hi,
>
> In preparation for a major exam tomorrow, I was just checking some of my
> answers to past-papers with mathematica, I fed it this input:
>
> In[117]:=
> \!\(\[Integral]\((xE\^\(2 x\))\) \[DifferentialD]x\)
> Out[117]=
> \!\(xE\^\(2\ x\)\/\(2\ Log[xE]\)\)
>
> I marked myself wrong and moved on to the next question, but I happened
> accross the actual mark-scheme which said I was correct. It gave this
> answer:
>
> ((1/2)xE^(2x))-(1/4)e^(2x)
>
> My Integral calculus isn't so strong, so I don't know if the additional
> natural log should be there, or if the two expressions are identical.
>
> Thanks



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