Tips | gCalcD

π: Ctrl+P or Alt+P or pi.
∞: Ctrl+8 or Alt+8 or infinity.
θ: Ctrl+T or Alt+T or theta. You can also use x or t instead of θ in polar mode; they will be replaced by θ when you press Draw Graph or Enter on the keyboard.

The quickest way to type domain= (-infinity, infinity) is by deleting the domain entirely (including domain=) and pressing Enter.

To graph a piecewise-defined function (or parametric curve) use the multi-graph window. Type in the number of pieces, and enter each piece with the corresponding sub-interval as a single function.