III. Working With A Graph
The ZOOM menu is a very useful tool when working with graphs.
The ZOOM menu offers you several preset windows and numerous other options. ZOOM can be a very powerful tool when analyzing a graph. There are many times when one of these options will work well with the function you are graphing. To access the ZOOM menu, press . Notice the small arrow at the far right of the menu. This means that the menu has more options, and you can access these by pressing the key.
BOX This allows you to box in a particular
area of the graph.
ZIN Zooms in with the center at the point
of the cursor. The default factor is 4.
ZOUT Zooms out with the center at the point
of the cursor. The default factor is 4.
ZSTD This is also a useful window. The window
size is X:[-10, 10] and Y:[-10, 10].
ZPREV Changes the window to the previous settings. ZFIT Sets a window that shows the maximum
and minimum value of Y with the given X window.
ZSQR Adjusts Xmin and Xmax so that the ticks
are the same distance apart on both axes.
ZTRIG Must be in radians. Preset to a window
that is good for elementary trig functions.
ZDECM This is one of the most useful windows.
It is also called a friendly window because
the TRACE key will move in increments of
0.1 with this window. The window size is
X:[-6.3,6.3] and Y:[-3.1, 3.1].
ZDATA Gives a window that shows all statistical
You can define zoom-window variables
using ZSTO and recall them with this option.
ZFACT Brings up the ZOOM FACTORS screen. ZOOMX Zooms out by a factor of xFact only
and disregards yFact.
ZOOMY Zooms out by a factor of yFact only
and disregards xFact.
ZINT Redefines the window to Xscl=10 and Yscl=10. ZSTO Stores the current window values that
can be recalled using ZRCL.
BOX: This is a very useful tool when you need to analyze a particular part of a graph and don't want to reset the WINDOW.
Example: Graph the function using ZDECM and then use BOX to examine the graph close to the origin.
The graph is close to the x-axis
around the origin, so using BOX
will help with the analyses.
Access BOX with
and you will
see the cursor
blinking at the origin.
Use the cursor keys to move
the cursor to the indicated
point and hit ENTER. You will see the cursor
change to a rectangle.
Once you hit enter,
that corner of the box
is anchored and cannot be moved.
Now move the cursor
to the indicated value.
Now hit ENTER and the
graph will be redrawn to show
only the part inside the box.
Press (ZPREV) and the
graph is restored
to the previous window.
ZIN: will zoom in on the graph with the position of the cursor serving as the new center. The default for ZIN is a factor of 4, but this can be changed by pressing .
Example: Use the function from the previous example to access the ZIN function. You can use ZPREV to restore the graph.
Graph the function.
Press and press
ENTER. You will see the
cursor blinking at the origin.
You can move the cursor to any
point that you want to be the
center of the new graph.
This has been left at the origin.
ZOUT: This works exactly like ZIN.
ZSTD: is a preset window of [-10,10] by [-10,10] with tick marks set at integers. The use of this window is demonstrated in the polynomial examples in the Setting Windows section.
ZPREV: See the example in BOX for the use of ZPREV. This will restore the previous window, and is useful after having used BOX, ZIN, or ZOUT.
ZFIT: will redraw the graph by resetting [yMin, yMax] to include the maximum and minimum values of the function over the interval [Xmin, Xmax]. This window can produce some rather distorted graphs and should be used with care.
ZSQR: will redraw the graph by adjusting [xMin,xMax] so that the tick marks are an equal distance apart on each axes. This is particularly useful when you need to see an accurate shape, such as a circle. ZDECM is also a square window.
EXAMPLE: Graph the circle by entering the functions and using ZSTD and ZSQR and compare the shapes.
Enter the functions. Use ZSTD. Use ZSQR.
ZTRIG: is a trigonometry preset window with [xMin,xMax]=. This option is covered in the trigonometry examples in the Setting Windows section.
ZDECM: is a "friendly window", which means that TRACE moves in increments of 0.1. This is a useful window to use when the graph will fit, because you can move to particular X-values easily. The use of this window is demonstrated in the polynomial examples in the Setting Windows section.
ZDATA: This option is not used in algebra, trigonometry, or calculus. It will primarily be used in statistics classes.
ZRCL: This option is used in conjunction with ZSTO. If you want to save window settings for later use, especially when ZPREV will not be useful, you can store your window by pressing ZSTO and then recall that window by pressing ZRCL.
ZFACT: Use this option if you want to change the zoom factors. The default setting is 4. This means that [xMin, xMax] or [yMin, yMax] are either multiplied by 4 with ZOUT or divided by 4 by ZIN.
ZOOMX: This will change the x-axis by the zoom factor, but will leave the y-axis alone. This could produce some rather strange graphs, so use this with care.
ZOOMY: This will change the y-axis by the zoom factor, but will leave the x-axis alone. This could produce some rather strange graphs, so use this with care.
ZINT: will redraw the graph and reset the window to Xscl=10 and Yscl=10. The TRACE key will move in increments of 1. To use this option, you must first draw the graph, press ZINT, and then press ENTER again.
ZDECM window. ZINT window.
ZSTO: See ZRCL.