       Re: Re: Simply derivative question, Math 5.

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• Subject: [mg50273] Re: [mg50257] Re: [mg50240] Simply derivative question, Math 5.
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Tue, 24 Aug 2004 06:22:08 -0400 (EDT)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200408220419.AAA10290@smc.vnet.net> <200408231034.GAA14653@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Typo: <Esc>ee<Esc>, not <Esc>e<Esc> (the latter yielding epsilon).

Murray Eisenberg wrote:

> As the Mathematica Book (printed or electronic) explains, ALL built-in
> objects in Mathematica have names that begin with an upper-case letter.
>   So the Napierian "e" is represented by E, not e.  (Or, if you want it
> to   look more like conventional mathematical notation, type Esc e Esc
> to obtain the Mathematica stylized e; in fact, you'll see that stylized
> e in the result.)
>
> So Mathematica was treating e as an unknown constant and gave the
>
> When e = E, then Log[e] = 1, so no "extra" factor:
>
>    D[(1 + c E^t)/(1 - c E^t), t] // Simplify
>
> By the way, you don't need an explicit multiplication operator after the
> c here -- just a space (so Mathematica can see you have two
> single-letter names rather than a two-letter name cE).
>
> It's REALLY worth a couple hours of your time to read the early material
> in the Mathematica Book!  It will save you a lot of time avoiding such
> basic difficulties.
>
>
> Ted Kahn wrote:
>
>>Hello- I am trying to take the derivative of the following function:
>>
>>(1 + c*e^t)/(1 - c*e^t)
>>
>>with respect to t.
>>
>>================
>>\!\(Simplify[D[\(1 + c\ e\^t\)\/\(1 - c\ e\^t\), t]]\)
>>============
>>
>>The answer I get includes an "extra" Log[e] in the numerator. Am I not
>>using the program correctly or am I not understanding the answer
>>correctly? Other?
>>
>>thanks, -ted
>
>

--
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

```

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