<p>"SAT OS" does not have polar coordinate support - (yet) => but I do know of an internal command on the TI-89 that would find the limit of your example. On the TI-89, there is a function called limit( => Simply type in your equation and it will find the limit of the equation. Also, to find the maximum and minimum values of an equation, just graph it and then hit max/min. on the MATH drop-down menu.</p>