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Re: Indefinate integrals, erroneus Natural log?

• To: mathgroup at smc.vnet.net
• Subject: [mg77901] Re: Indefinate integrals, erroneus Natural log?
• From: nazdrovje at gmail.com
• Date: Tue, 19 Jun 2007 06:42:47 -0400 (EDT)
• References: <f55oor$j6f$1@smc.vnet.net>

Both answers are OK. You seem to have entered or formatted them wrong.

The integral should be entered as
\[Integral](x \[ExponentialE]^(2 x)) \[DifferentialD]x

the textbook answer should be entered as
((1/2) x \[ExponentialE]^(2 x)) - (1/4) \[ExponentialE]^(2 x)

Equating both and using FullSimplify results in equality.

you merged the x and E (put a space between them). the exponential-e
can be entered as esc+ee+esc.

Cheers,

Naz

On Jun 18, 1:02 pm, "David Rees" <w3bdevilREM... at THISw3bdevil.com>
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