This first step is not necessary. The only purpose of step 1 is to
graph the original function. If you only want to draw the graph of the inverse of the function skip to steps 2 and 3


Step 1) Graph a function as you would normally
Click on the 'y=' button and then type any math function (we will use y = x² +2x +1 in our example)
Press the graph button and you will see the function graphed (in our case a parabola's graph ) 

Step 2) To graph the inverse of whatever function is currently graphed. Press the following sequence of buttons
 2^{nd} button (on top left of graphing calculator)
 the 'DRAW' button which is immediately under the STAT in the TI83 and TI84 (at this point you should see the image on the right)
 Scroll down to 8 "DrawInv" which of course stands for drawing the inverse of the function


Step 3) press 'enter'
Enter the function whose inverse you want to draw, which for us is this equation of a parabola :y =x² + 2x +1


Press 'enter' then hit 'graph' to see the graph! 

To clear the graph of an inverse from your Ti 's graph screen
, press the following four buttons
2nd
Draw
1
enter 
