Each function can have its own domain. These are entered by pressing the f(x) button (the first function's domain can be entered on the graph screen). Domains are entered the way you would normally write them (in terms of x or t).
For example
x > 2 t <= 4 -3 < x <=7
Alternatively you can use the bracket notation for domain
For example
y = x2 [-2,3)
will produce
