Texas Instruments PLUS TI-89 - Manual (Page 355)

338 Chapter 19: Numeric Solver
19SOLVER.DOC TI-89/TI-92 Plus: Numeric Solver (English) Susan Gullord Revised: 02/23/01 1:16 PM Printed: 02/23/01 2:19 PM Page 338 of 10
¦ If the equation contains a
system variable (
xmin , xmax ,
etc.), that variable is not
listed. The solver uses the
system variable’s existing
value.
¦ Although you can use a
system variable in the
equation, an error occurs if
you use … to graph the
solution.
¦ If you see the error shown
to the right, delete the
entered variable value. Then
edit the equation to use a
different variable.
In the Numeric Solver, press C until the cursor is on the equation.
The screen automatically changes to show only the
eqn: line. Make
your changes, and then press ¸ or D to return to the list of
variables.
To find a solution more quickly or to find a particular solution
(if multiple solutions exist), you can optionally:
¦ Enter an initial guess for
the unknown variable.
The guess must be within
the specified bounds.
¦ Enter lower and upper
bounds close to the
solution.
For the bounds, you can also enter variables or expressions that
evaluate to appropriate values (
bound={ lower , upper } ) or a valid list
variable that contains a two-element list ( bound= list ). The bounds
must be two floating point elements with the first one less than or
equal to the second one.
Note: You cannot solve for
a system variable other than
exp
. Also, if the equation
contains a system variable,
you cannot use
… to graph.
Note: This error occurs if
you use a reserved name
incorrectly or refer to an
undefined system function
as a simple variable without
parentheses.
Editing the Equation
Specifying an Initial
Guess and/or
Bounds (Optional)
Tip: To select an initial
guess graphically, refer to
pages 340 and 341.
For example, y1(x) is undefined
and you use y1.
Initial guess must be
within the bounds.
In the standard viewing window,
xmax=10.