Re: Re: Forcing a Derivative

• To: mathgroup at smc.vnet.net
• Subject: [mg50793] Re: [mg50778] Re: Forcing a Derivative
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Tue, 21 Sep 2004 03:49:18 -0400 (EDT)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <cijej8\$hlp\$1@smc.vnet.net> <200409200139.VAA27554@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Your answer, and those of others, just reinforces my complaint about
this limitation of Mathematica today.  Why should one have to introduce
what is, from a modern mathematical point of view, an extraneous extra
variable, "x"?

A function f is an object; an "expression in x" such as f[x] is quite
another.  Or at least it should be!

Klaus G wrote:

>>...
>>Derivative[2][f * g]
>>just puts a couple of primes on the product rather than actually computing the dervative.
>>Thanks for any insight.
>>Cheers, Scott
>
>
> Hi,
>
> f is NOT f[x], so please try:
>
> deriv = D[f[x]*g[x], {x, 2}]
> Collect[deriv, x]
>
> regards
> Klaus G.
>
>

--
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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