Graphing calculators are calculators that can plot graphs and even solve equations. They make your math adventure easier by doing some of the work for you. Is not that great? The bottom line is that you need to know how to tell them what you want them to do. Graphing calculators are packed with functions and there are many models. This tutorial may not cover all of them or come close to explaining all the functions of any of them. But it will give you an idea of the basic functions of a graphing calculator. We will be using the TI-89 as our base model. From there, you can extrapolate to other types of graphing calculators.
Plotting a graph
Let’s start with the most basic and recognizable function of a graphing calculator: plotting. Seems appropriate, right? You can do this using the following steps:
1. Turn on the calculator by pressing the “On” button at the bottom left of the calculator.
2. Then press the green diamond button in the upper left corner, then “F1”. This will take you to a screen that shows where you can enter the equation for your graph.
3. For simplicity, why don’t we plot y = x? Just press the “x” key and then the “Enter” key in the lower right corner of the calculator.
4. Then press the green diamond button again and then press “F3”. This will take you to your very first graph, where y = x! You should see a diagonal line running right through the origin where the horizontal and vertical axes intersect.
Finding the intersection
Now let’s do something a little more complex. Return to the screen where you entered the equation for your graph (hint: press the green diamond button and F1). Next to where it says “y2”, enter “-x” (keep the original y1 = x). Now go back to the chart by pressing the green diamond button and then F3. You should see another line through the intersection.
You can see that both lines go through the intersection of the horizontal and vertical axes, so they intersect at the point (0,0). But how can we show this on a calculator? Well, in order for the calculator to confirm that this is where the two lines intersect, follow these steps:
1. From the graph screen (where all the lines are drawn), press “F5”.
2. This will bring up a drop-down menu. See where the intersection is written? Press “5” to select it.
3. On the screen, you will see a calculator with the question “1st curve?”. Just hit Enter.
4. On the screen, you will see a calculator with the question “2nd curve?”. Just hit Enter again.
5. Now the calculator asks you for “Lower Boundary?” Use the arrow keys (top right on the calculator) to move the cursor down on the graph to a point to the left of the intersection. Press Enter.
6. Now the calculator asks you “Upper limit?” Use the arrow keys (in the upper right corner of the calculator) to move the cursor up on the graph to the point to the right of the intersection.