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>*Reply-to*: murray at math.umass.edu*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

**Follow-Ups**:**Re: Re: Re: Forcing a Derivative***From:*Andrzej Kozlowski <andrzej@akikoz.net>

**References**:**Re: Forcing a Derivative***From:*Karl_boehme_9@msn.com (Klaus G)