If I set up a graph, say y=tan(x) and my x-axis is in units of pi, I can't seem to enter an definite integral which involves the symbol of pi in the limits. To integrate from 0 to pi/4, I have to actually enter the upper limit by multiplying the value of pi and 1/4. I can't access the symbol when I am in the process of integrating, and the program won't accept a typed in pi. I would appreciate advice. Thanks.