Re: imposing parameter assumptions

*To*: mathgroup at smc.vnet.net*Subject*: [mg44198] Re: imposing parameter assumptions*From*: bobhanlon at aol.com (Bob Hanlon)*Date*: Sun, 26 Oct 2003 00:41:52 -0400 (EDT)*References*: <bndkco$g6f$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Use Simplify f[a]=a^-3; Simplify[#[f[a]], a<0]& /@ {Sign, Positive, Negative, NonNegative} {-1,False,True,False} Bob Hanlon In article <bndkco$g6f$1 at smc.vnet.net>, "drr7" <rondeau at uvic.ca> wrote: << Simple question: How do I impose assumptions on the sign of parameters in symbolic equations and then test for the sign of an expression. Example: suppose I want to test the sign of f[a]=a^-3 if a<0. I tried combinations of Refine and Positive, but that does not seem to work for me. What I am really trying to do is sign a long expression for a derivative. >><BR><BR>