Solution 30531: Finding the Inverse of a Function on the TI-89 Family, TI-92 Family and Voyage™ 200 Graphing Calculators.
How do I find the inverse of a function on a TI-89 Family, TI-92 Family and Voyage 200 calculator?
For example, if you need to find the inverse of f(x)=5/x+10 follow the steps listed below.
1) On a sheet of paper, replace x with y, and replace f(x) with x
2) Your equation should now be x=5/y+10
3) Solve for y using your calculator by pressing: [F2] [ENTER] [x] [=]  [/] [y] [+]   [,] [y] [)]
Please see the TI-89 family, TI-92 family and Voyage 200 guidebooks for additional information.