Assumptions about variables
- To: mathgroup at smc.vnet.net
- Subject: [mg30727] Assumptions about variables
- From: "Jacek Dziedzic" <dust at tenbit.pl>
- Date: Sat, 8 Sep 2001 02:56:13 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Hello all! Can someone please tell me how do I tell mathematica (3.0) to assume certain things about variables, for example that they are positive or are contained in a range such as <3,4). In Derive you could declare a variable as "positive" and it was very easy. The only thing I found out until now is how to let it know that a variable is real, I do it like this: a /: Im[a] = 0 (for a variable a). Things like a /: Sign[a] = 1 don't do what I want. As an example I have a partial differential equation that has a soliton solution only when a parameter is positive. How do I tell the mathematica to assume that this parameter must be positive? Thanks in advance.