To plot things surfaces $f(x,y,z)=$ constant in x,y,z space use the "implicit plot" command. Use "==" (double equal signs) for the equal sign. It's necessary to start by telling Sage that $x,y$ and $z$ are variables. That's what the "var" command does.

Here are some examples from the text. You can rotate the figures with your mouse to see if from different points of view.

3D rendering not yet implemented

3D rendering not yet implemented

3D rendering not yet implemented