Editing the equation – Texas Instruments TI-86 User Manual
Page 217
Chapter 15: Equation Solving
205
15EQSOLV.DOC TI-86, Chap 15, US English Bob Fedorisko Revised: 02/13/01 2:34 PM Printed: 02/13/01 3:04 PM Page 205 of 12
15EQSOLV.DOC TI-86, Chap 15, US English Bob Fedorisko Revised: 02/13/01 2:34 PM Printed: 02/13/01 3:04 PM Page 205 of 12
The TI
-86 solves equations through an iterative process. To control that process, you can
enter lower bounds and upper bounds that are close to the solution, and enter a guess
within those bounds in the prompt for the unknown variable.
Controlling the process with specific bounds and a guess helps the TI
-86 in two ways.
♦
It finds a solution more quickly.
♦
It is more likely to find the solution you want when an equation has multiple solutions.
To set more precise bounds at the
bound=
prompt, the syntax is:
bound={
lowerBound
,
upperBound
}
At the prompt for the unknown variable, you may enter a guess or a list of two guesses. If
you do not enter a guess, the TI
-86 uses (lowerBound+upperBound)à2 as a guess.
On the solver graph (page 207), you can guess a solution by moving the free-moving cursor
or trace cursor to a point on the graph between lowerBound and upperBound. To solve for
the unknown variable using the new guess, select
SOLVE
from the solver graph menu. The
solution is displayed on the interactive-solver editor.
Editing the Equation
To edit the equation stored to
eqn
when the interactive-solver editor is displayed, press $
until the cursor is on the equation. The equation-entry editor is displayed. The TI
-86
automatically stores the edited equation to
eqn
as you edit.
If you store an equation to
eqn
by recalling the contents of an equation variable, such as
y1
,
and then edit the equation stored to
eqn
, the original equation (in
y1
, for example) is not
changed. Likewise, subsequently editing the contents of the equation variable (
y1
, for
example) does not change
eqn
.
lowerBound
<
upperBound
must be true.
You can enter a list variable
at the bound= prompt if a
valid two-element list is
stored to it.
If you exit the equation
solver, any equation stored to
eqn is displayed when you
return to the equation solver.