I frequently use Google's ability to plot functions to get a quick view of what a function looks like, for example: sin(x), x^3.
However, some operators that work when given a number, like 3! * x, which plots 6*x, don't seem to work when applied to the x variable: 3! * x! doesn't give a plot at all.
I have failed to use the factorial operator (x!), and the modulous operator (x mod 3).
Is there a reference, documentation or whatever specifying the syntax for google's graphical calculator? I know it can do some pretty advanced things like plot functions in 3D over a specified range, but trying to use these features by hitting at random in the dark is kind of sub-optimal.