Texas Instruments TITANIUM TI-89 - Manual (Page 428)

Differential Equation Graphing 428
Example Example Example Example
1. Press 3 and set
Graph=DIFF EQUATIONS .
2. Define a system of equations for the 2nd-
order equation.
Rewrite the equation and make the
necessary substitutions.
3. In the Y= Editor ( 8 #), enter the
system of equations.
4. Enter the initial conditions:
yi1=0 and yi2=1
Note: t0 is the time at which the initial
conditions occur. It is also the first t
evaluated for the graph. By default,
t0=0 .
5. Press:
,
9
— or —
@ 8 Í and set
Axes = ON , Labels =
OFF , Solution Method = RK , and
Fields = DIRFLD .
Important: For 2nd-order equations, you
must set Fields=DIRFLD or FLDOFF .
y'' + y = 0
y'' =
L y
y'' = L y1
y2' = L y1
yi1 is the initial
condition for y(0).
yi2 is the initial
condition for y'(0).