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## HOW TO GRAPH SOLUTION CURVES TO DIFFERENTIAL EQUATIONS WITH TI89 CALCULATOR

 Example: Graph the solution curve for the differential equation: y ′ = x – y, y(1) = 0. Steps Key Sequence Screens 1. Graph Slope Field 2. Enter Initial Conditions Press Diamond key, then F1 (for Y=) NOTE: y(1) = 0 means y = 0 when t = 1. Press up arrow (to t0=0) Press ENTER, then 1, then ENTER Press down arrow (to yi1=) Press 0, then ENTER 3. Graph the Solution Curve Press Diamond key, then F3 key NOTE: You can graph more than one solution curve when t0=1 at the same time. In addition to the above solution curve, graph the solution with the initial condition y(1) = 2. 4. Enter Both Initial Conditions Press Diamond key, then F1 (for Y=) Press up arrow (to yi1=) Press ENTER, then 2nd, then ( key Press 0, then comma key, then 2, then 2nd, then ) key, then ENTER 5. Graph the Solution Curves Press Diamond key, then F3 key ALTERNATIVELY: You can graph more than one solution curve by using the F8 (i.e., IC) menu. For example, graph the solution curve for the initial condition y(5) = –1. 6. Graph an additional Solution Curve Press 2nd, then F3 key (for F8) Press 5, then ENTER (for t = 5) Press (–), then 1, then ENTER (for y = –1) NOTE: You can delete the manully-graphed solution curves by pressing F4.