Defining derivatives

*To*: mathgroup at smc.vnet.net*Subject*: [mg87851] Defining derivatives*From*: dh <dh at metrohm.ch>*Date*: Fri, 18 Apr 2008 07:11:33 -0400 (EDT)

Hello All, does anybody know how to define symbolic derivatives. E.g.: f[x_]:=f1[x]; f'[x_]:=f2[x]; this does not work because f on the lefthand side is evaluated. To prevent this (do not forget to remove f before redefining it): f[x_]:=f1[x]; HoldPattern[f'[x_]]:=f2[x]; this gives no message, but f'[x] returns f1[x] instead of f2[x]. The same thinhg happens when you change the sequence of definitions: f'[x_]:=f2[x]; f[x_]:=f1[x]; Further, where is the information about derivatives stored? thank's a lot, Daniel

**Follow-Ups**:**Re: Defining derivatives***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**Re: Defining derivatives***From:*Carl Woll <carlw@wolfram.com>