Sign Query
- To: mathgroup at smc.vnet.net
- Subject: [mg19728] Sign Query
- From: David Ridley <dbr1 at duke.edu>
- Date: Mon, 13 Sep 1999 02:40:58 -0400
- Organization: Duke University, Durham, NC, USA
- Sender: owner-wri-mathgroup at wolfram.com
Hello, Please excuse my ignorance. I'm trying to sign a function and wonder how to go about making some assumptions. In general, my problem is as follows: a=b-c Sign[a] I know that b<0 and c>0. How do I tell Mathematica? ------- More specifically, my problem is the following: focp=(-(1+r)Q1[P]-(1+g)Q2[(1+g)P]+c(1+r)Q1'[P]+c(1+g)Q2'[(1+g)P]) /((1+r)Q1'[P]+(1+g)^2Q2'[(1+g)P]) dpdg=Simplify[D[focp,g]] Sign[dpdg] where: c,g,r,P,Q1,Q2 >0 Q1',Q2'<0 Q1", Q2" ??? ----- Thank you very much for any help that you might be willing to provide. Regards, David Ridley