[Date Index] [Thread Index] [Author Index]

Re: Re: Simply derivative question, Math 5.

• To: mathgroup at smc.vnet.net
• 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>
• Reply-to: murray at math.umass.edu
• 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 
> correct answer.
> 
> 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

• References:
  • Simply derivative question, Math 5.
    • From: "Ted Kahn" <tedkahn@mindspring.com>
  • Re: Simply derivative question, Math 5.
    • From: Murray Eisenberg <murray@math.umass.edu>