How to set y always greater than or equal to x for a function?

*To*: mathgroup at smc.vnet.net*Subject*: [mg46569] How to set y always greater than or equal to x for a function?*From*: Albert Franco <francoatnsuok at earthlink.net>*Date*: Mon, 23 Feb 2004 22:33:55 -0500 (EST)*Organization*: The Franco Family*Reply-to*: francoatnsuok at earthlink.net*Sender*: owner-wri-mathgroup at wolfram.com

I recently purchased Mathematica 5.0, and I am in the process of learning how to take advantage of it's many features. This is an example of one line I would like to calculate in Mathematica: Plot3D[Sqrt[y-x],{x,-100,100},{y,-100,100}]; How can I best edit this line to make y always greater than or equal to x during calculation so the program doesn't try to take the square root of a negative number? Any help will be appreciated. Albert Franco

**Follow-Ups**:**Re: How to set y always greater than or equal to x for a function?***From:*Oleksandr Pavlyk <pavlyk@phys.psu.edu>