I'll note for the record that there are many other very interesting articles about mathematics living at that site,<p><a href="http://www.dpmms.cam.ac.uk/~wtg10/" rel="nofollow">http://www.dpmms.cam.ac.uk/~wtg10/</a><p>the academic home page for Timothy Gowers.
If R^3 is taken with vector (x1,x2,x3) defined using x1+x2+x3=0 then I can't quite picture that, I can only imagine the projections on the axes, not the actual plane ... anyone know of a simply 3D graphing tool online.