Texas Instruments TI-82 Keystroke Manual page 26

All of this may look rather complicated, but perhaps an example or two will help you see how
it works. As a beginning example, suppose you want to shade the solutions of the inequality
2
≤ −
y x 4 . One way to do this is first to enter the corresponding equation
3
the Y= screen. (Enter the equation as Y
the Standard viewing window, just to see what it looks like and to see if the Window settings give
a good view of the graph. Press 2nd [QUIT] to return to the Home screen. The solution of the
inequality consists of all points on or below the graph of the equation, since for each value of x,
the values of y must be less than (below) or equal to (on) the values of y on the graph. Therefore,
the graph of the equation will form the top of the shaded region indicating the solution of the
will be your upper function on the Shade command. All points below the graph
inequality. Thus, Y
1
of Y are part of the solution of the inequality, so there really is no bottom to the shaded region.
1
For the purposes of the Shade command, you want the shading to go to the bottom of the graphing
window, so you can use the any number below lowest value of y displayed, Ymin, as the lower
function. Really, lower function and upper function are the only two quantities needed to do a basic
shading. At the Home screen press 2nd [DRAW] to display the general DRAW menu. Press 7 to
display the Shade( command on the Home screen. Note that the Shade( command automatically
displays an open parenthesis to save you a bit of typing. The first thing you must enter is the lower
function. Since the lowest value of y in the Standard viewing window (Ymin) is −10, type in
anything less, such as −11. At the Home screen you should now see Shade(-11. Before you
enter the upper function, you must type in a comma to separate it from the lower function. (The
comma key is just above the 7 key.) The upper function is Y
to choose the Function... menu, and then press 1 or ENTER to choose Y
at the end to complete the command. At the Home screen you should now see Shade(-11,Y
Press ENTER to execute the Shade command. The calculator should display the graph with solid
shading below the line.
If you want to erase this shading, press 2nd [DRAW] and then choose 1 (ClrDraw). If you select
this command from the Home screen, the command ClrDraw (Clear Drawing) will be displayed at
the Home screen. Press ENTER to execute the command. The calculator will respond with the
word Done. Press GRAPH to verify that the shading has been erased. If you have done some
shading and are viewing the Graph screen when you select the ClrDraw command (2nd [DRAW], 1),
the calculator will immediately return to the Graph screen and redraw the graphs without the
shading.
To graph the solutions of the inequality
the Standard viewing window (or any other convenient graphing window). This time, all points
=
above the line y 2 x are solutions of the inequality. Thus, the graph of the line forms the bottom
=(2/3)X-4.) You may want to graph this equation in
1
, so press 2nd [Y-VARS], press ENTER
1
>
y 2 x , enter as Y
TI-82
2
= −
y x 4
3
. Type a close parenthesis
1
=
the equation y 2 x . Graph it in
1
21
as Y on
1
).
1