The FnOff command is used to turn off equations in the current graphing mode. When you turn off an equation, it's still defined, but isn't graphed; you can reverse this with the FnOn command. To turn functions on and off manually, put your cursor over the = symbol in the equation editor, and press enter.
When FnOff is used by itself, it will turn off all defined equations in the current graphing mode. You can also specify which equations to turn off, by writing their numbers after FnOff: for example, FnOff 1 will turn off the first equation, and FnOff 2,3,4,5 will off turn the second, third, fourth, and fifth. The numbers you give FnOff have to be valid equation numbers in the graphing mode. When turning equations on and off in sequence mode, use 1 for u, 2 for v, and 3 for w.
The most common use for FnOn and FnOff is to disable functions when running a program, so that they won't interfere with what you're doing on the graph screen, then enable them again when you're done.
- ERR:DOMAIN is thrown if an equation number isn't valid in the current graphing mode, or at all.