Integrals on your Ti-89
Check out my "Derivatives" section, doing integrals are exactly the same just use the integral button (which is 2nd->"7") instead of the derivative.
If you are doing a definite integral, after the variable you want to integrate at the end (like normal, before the final parenthesis), put another comma, then put the initial value, comma, final value, close parenthesis. [ie to evaluate the equation (from the "Derivative" section) from 1 to 2, type 2nd->"7"(0.5x^2,x,1,2) -> "enter" and you should get 1.16667]
check out Calcblog's treatment of the subject in a new window
and youtube video's!