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Re: Re: bug? f'[x]'

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90935] Re: [mg90914] Re: [mg90894] bug? f'[x]'
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Wed, 30 Jul 2008 03:53:11 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <22482780.1217263035440.JavaMail.root@m08> <200807290539.BAA18274@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Perhaps the actual trouble is that notations like f[x]' are in effect 
used all the time in traditional math notation.  For example:

    (3x^2 + 5x - 8)' = 6x + 5,
    (sin x)' = cos x,
     (e^x)' = e^x

Go look in just about any beginning calculus book.

No wonder students don't understand calculus and functions when such 
clap-trap is taught.

DrMajorBob wrote:
> The right side of both equations is meaningless in Mathematica, so of  
> course they are not True.
> 
> For a version of the second one, we do have
> 
> D[f'[x], x] == f''[x]
> 
> True
> 
> Bobby
> 
> On Mon, 28 Jul 2008 06:53:58 -0500, <Benjamin.R.Lewis at gmail.com> wrote:
> 
>> G'day,
>>
>> In[]:= f'[x] =!= f[x]' && f''[x] === f'[x]'
>> Out[]= True
>>
>> Can anyone explain this?
>>
>> -Ben
>>
>>
> 
> 
> 

-- 
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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