This can be used to evaluate the expression currently in the window. It does NOT work on equations ( ie if there is an equals sign in the expression then this function will always return zero ). The program will need to know what values to substitute in for any variables used in the expression. When you have entered these then press "EVALUATE" and the expression will be calculated. There is also the option to graph the function. The graph works on the same values for variables as the evaluator.