Graphing D.E.s on the TI-82 - an example

Prof. Janeba

Here is a step-by-step example for graphing a system of differential equations on the TI-82.

Consider this problem:

Suppose we want to plot x vs y (a phase-plane image) with 0x60000 and 0y21500 for 0t50.

Enter dx/dt in y1 and dy/dt in y2:
After deciding what you want plotted on each axis, set your range:
Press [PRGM] and select the program DESYSTM. Press [ENTER] once to get:
Press [ENTER] again to get:
Enter intial values of t, x, and y:
Press [ENTER] and then give final values for t and the number of steps to plot:
When you are done with that, you will get a menu to choose the axes for your plot:
We had chosen x vs. y above, so we press 1 here. You don't need to press [ENTER]. The plot you have chosen is now drawn:
To find the final (approximate) values of x, y, and t, type "X [ENTER]", "Y [ENTER]", and "T [ENTER]"

You can re-run the program to see the other axes options; remember that you will probably have to change the viewing window when you change what variable is plotted along each axis. When you re-run the program, you can enter "A" for initial x, and "B" for initial y to reuse the previous settings.

Please mail comments or questions to: mjanebawillamette.edu

Return to Prof. Janeba's Home Page

Willamette University Home Page