EULER

TI 81

-This program plots an approximate solution for the differential equation ${\hbox{dy}\over \hbox{dx}}=\hbox{f(x,y)}$ using Euler's method. The program will ask for initial point and step size. Solutions can be superimposed on a slopefield by running the Slopefield program first. Previous are not cleared.

Note: Information in {} is not put into the calculator. Information in RED denotes a button on the calculator

Note: Information like BLUE(RED) means to access BLUE hit 2ed then RED

The pause command in the program allow you to see the solution in segments. Use ENTER to continue, ON to quit.
An expression for f(x,y) must also be entered before running this program. For x use X|T. For Y use ALPHA then Y.

:All-Off

:Disp "INITIAL X"

:Input X

:Disp "INITIAL Y"

:Input Y

:Disp "STEP SIZE"

:Input H

:Lbl 1

:0 $\to$ C

:Lbl 2

:X+H $\to$ U

:Y+Y1*H $\to$ V

:Line(X,Y,U,V)

:U $\to$ X

:V $\to$ Y

:IS>(C,20)

:Goto 2

:Pause

:Goto 1

{All-Off is found with Y-VARS(VARS) in the OFF Menu}

{Disp is found with PRGM in the I/O Menu}

{Input is found with PRGM in the I/O Menu}

{Lbl if found with PRGM in the CTL Menu}

{The 0 is a zero}{The arrow is STO}

{Y1 is found with Y-VARS(VARS)}

{Line is found in DRAW(PRGM) in the Draw Menu}

{IS> is found with PRGM in the CTL Menu}

{Goto is found with PRGM in the CTL Menu}

{Pause is found with PRGM in the CTL Menu}