1. Is it possible for the TI-89 to solve Exact Equations? Ex: (2x-1)dx + (3y+7)dy = 0 I've tried various forms of input, but I cannot find a way for the Calculator to give me a complete answer. My best luck so far was: (2x-1)x' + (3y+7)y' = 0. The y' part was correct, the x' part was incomplete. 2. I've been reading about how to convert higher order equations into a form that the calculator can solve. Ex: y''' + 3y'' + 2y' - 5y = sin(2t) Can be written as: y'(subscript 3) = 5y(subscript 1) - 2y(subscript 2) -3y(subscript 3) + sin(2t) How might I enter this into the TI-89? 3. Why does the TI-89 put tan and cot in terms of sin and cos? I have seen rather simple equations turn into complicated messes because of this. Thanks in advance.