The TI-92 program below -- vs1 -- can be used to draw slope fields for differential equations of the form

Skip ahead if this program is already in your TI-92. If not, enter it in the usual way by typing it in or by downloading it using the TI-Graph Link.

There have been numerous problems downloading programs for TI graphing calculators using the method above. If that method works, it is very clean. Sometimes, however, it doesn't work. In that case we can fall back on an older method, uuencoding, that is less user-friendly but more reliable. Click here for more information about this method. Then click here for a uuencoded (text file).

The TI-92 graphics mode must be set to function for this module. The first step in drawing the slope field for a differential equation of the form y' = f(t, y) is to define the function on the right hand side of the differential equation. The screen at the right shows how this is done. Notice the function must be called vsf and it must have two arguments, even if only one is used. The first argument must be the independent variable and the second argument must be the dependent variable.
The next step is to set the range of the independent variable and the dependent variable in the window screen as shown at the right.
Finally, execute vs1() from the home screen as shown at the right.
to see a slope field like the one shown at the right.
You can combine the usual TI-92 graphing features with this program. For example, suppose that you are examining the differential equation y' = sin t - y which might be a variation of Newton's Model of Cooling with the ambient temperature A(t) = sin t.
You can graph the slope field in the usual way as shown in the sequence of screens at the right.
Then you can superimpose the graph of the ambient temperature by entering the appropriate function in the Y= screen
and then pressing green-diamond GRAPH.