Some little AP Tidbits. I will add as I learn new ones...

1.  When performing a numerical integration on the calculator, you can either use MATH 9: fnInt( function, x, a, b) OR CALC 7:.  The suggestion from gurus smarter than me is that you use the first option.  Much more accurate.

2.  when doing u substitution you really should change the limits of integration.... but the solution if you do not plan on staying in "u" (go back to x) is to write the new lower limit as x = a and the new upper limit as x = b.