Texas Instruments TI-83 Plus Manual Book page 14

Y= Editor and X= Editor
When you place the cursor over the equality symbol on the
Y= editor, you immediately see some of the features the
Inequality Graphing application offers. A set of relation options is
inequality symbol (>, <, | , { ) as well as the equality symbol.
displayed across the bottom of the screen. You can use any
(These options are displayed only when the cursor is over the
relation symbol.)
The Inequality Graphing application has an X=editor to
complement the Y=editor. You access it from the Y=editor and
you can move between the two editors as much as you like. A
highlighted
you that you defined and selected equations or inequalities on
the other editor.
On the X= editor, an expression must evaluate to a real number.
You can use any constant function of
whether they are equations or inequalities.
Inequality Graphing for the TI-83 Plus
or in the top left corner of the screen reminds
X= Y=
to define vertical lines,
X
Page 14