Texas Instruments TI-89 Voyage 200, User Manual

Page: 436 / 1008

Differential Equation Graphing 436
Predator-Prey Model
Predator-Prey Model Predator-Prey Model
Predator-Prey Model
Use the two coupled 1st-order differential equations:
y1' =
L
y1 + 0.1y1
ù
y2 and y2' = 3y2
N
y1
ù
y2
where:
y1 = Population of foxes
yi1 = Initial population of foxes (2)
y2 = Population of rabbits
yi2 = Initial population of rabbits (5)
1. Use
3
to set
Graph = DIFF
EQUATIONS
.
2. In the Y= Editor (
8 #
), define the
differential equations and enter the
initial conditions.
Note:
To speed up graphing times, clear
any other equations in the Y= Editor. With
FLDOFF
, all equations are evaluated even
if they are not selected.
3. Press:
,
9
— or —
@ 8
Í
Set
Axes = ON
,
Labels = ON
,
Solution Method = RK
, and
Fields = FLDOFF
.