Slopefields on the TI-86

Given a differential equation, say y' = 3x-y, here is how to make the TI-86 draw a slopefield for that differential equation.
  1. Put the calculator into Differential Equation mode: Press [2nd] [MODE] and select DifEq as shown:

  2. We must translate the differential equation: In place of the function (y in this case), write Q1, and in place of the variable (x in this case), write t. So we get

  3. Q1' = 3t-Q1, or as the calculator wants it, Q'1=3t-Q1.
  4. Now press [GRAPH][Q'(t)=] and enter our differential equation from the last step on the first line:

  5. Press [EXIT][MORE][FORMT] and make sure that, at the bottom of the screen, both SlpFld is selected:

  6. Finally, press [WIND] to select a suitable window: (Set x and y ranges as usual; you can ignore t for now), and then press [GRAPH].

Last Modified December 7, 1998.
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