# Introduction to the Graphing Display Calculator (GDC)

This section covers:

Note: Graphing Quadratics on the graphing calculator can be found in the Using the Graphing Calculator to Find the Vertex and Solve Quadratics in the Introduction to Quadratics section. Graphing Trigonometric Functions on the graphing calculator can be found in the Trig Functions in the Graphing Calculator in the Graphs of Trig Functions section.

Beginning with your first Algebra course, you’ll probably get introduced to a graphic display calculator or graphing display calculator (GDC). I prefer the Texas Instruments® TI-83 or TI-84 Plus. The software I’ve used to create these graphs is the “online” version of this calculator, TI-SmartView™ Emulator Software for the TI-84 Plus Family, which can be downloaded from the Texas Instruments web site.

Note: most pictures show the TI-84 C (Color) Silver Edition calculator.

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First, turn the calculator ON, and make sure the calculator is in FUNC mode (for “function”): hit MODE (in the upper left – to the right of the 2nd button). On the 4th line, make sure FUNC is highlighted:

Note: To make your TI-84 C calculator graph a little faster, hit , scroll down to “Detect Asymptote” and turn this Off:

Note:  If your graphing calculator ever gets “stuck” and doesn’t seem to be graphing, you can hit  to turn it off, and then   to turn it back on again.

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Also, if you need to clear (reset) the calculator, you can use    to clear the RAM in the calculator. But be careful doing this, since you will lose any programs you’ve created in the calculator.

# Basic Graphing

To create the graph “$$y=10x$$”, press the following.

You may need to press CLEAR to clear out any equations in any of the “Y=” fields.

You can put additional equations in “Y2=” and so on. It’s as easy as that!

You have to be careful when you look at these graphs, since the scales may not be what you want. Note that the $$x$$-axis has a different scale than the $$y$$-axis.

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If you don’t see the graph in the middle of the screen, you can enter ZOOM  6 (ZStandard)to get the standard window (typically –10 to 10 on both axes). You can also use the cursors to move down to ZStandard after you press ZOOM.

If you still don’t see what you want in the graph, try ZOOM 0 (ZoomFit), or go to WINDOW and enter appropriate values for Xmin, Xmax, Ymin, and Ymax, by looking at your graph and seeing what axis or axes you need to make larger or smaller. I would leave Xscl = 1.

For example, in the graph above, we may want to reduce the size of the X window to see more of the graph. The Xmin was changed from “–10” to “–4”, and the Xmax was changed from “10” to “4”.

Also note that the graph is not square; the $$x$$-axis is scaled differently than the $$y$$-axis. You can make the graph square by trying ZOOM 5 (ZSquare).

You can hit TRACE and move the cursors to see the different values of $$x$$ and $$y$$ on the graph.

You can also go to the TABLE (2nd GRAPH) to see actual points, and scroll up and down with the cursor. If you want to start from a different point, or want to change the delta X (how often the $$x$$ values are displayed, for example, by 1’s or by .5’s), you push TBLSET (2nd WINDOW):

(Note that it gets a little more complicated if you want graph a vertical line like “$$x=3$$”; you can do this with another mode (PAR), but you usually won’t be graphing these vertical lines).

# Inequalities

We can also display inequalities on the calculator.  Use “Y=” to input the equation in the calculator, and then use the cursor   to scroll left to the “Y=”.  When the cursor is over the “\”, hit ENTER until you see  (for less than) or  (for more than).   (For the TI-84 C Calculator), you’ll have to scroll down over where you can change the colors). You can put more than one inequality by using “Y2=” and so on.

To put the graphing calculator back to “=”, hit ENTER the same way until you see “\” again.

Here’s an example for $$y<2x+4$$ and $$y>3$$:

This should give you a start in getting familiar with the graphing calculator; I will provide more instructions in each section where we use it.

Practice on the Graphing Calculator – you can’t hurt it!

On to  Algebra Word Problems – you are ready!

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