# How to Trace a Graph on the TI-84 Plus

Tracing a graph on the TI-84 Plus graphing calculator shows you the coordinates of the points that make up the graph. After you have graphed your function, you can press **[TRACE]** and then use

and

to more closely investigate the function.

If you use only the

keys instead of **[TRACE]** to locate a point on a graph, all you will get is an *approximation* of the location of that point. You rarely get an actual point on the graph. So always use **[TRACE]** to identify points on a graph.

The following list describes what you see, or don’t see, as you trace a graph:

**The definition of the function:**The function you’re tracing is displayed at the top of the screen, provided the calculator is in**ExprOn**format. If the Format menu is set to**ExprOff**and**CoordOn**, then the Y= editor number of the function appears at the top right of the screen.If the Format menu is set to

**ExprOff**and**CoordOff**, then tracing the graph is useless because all you see is a cursor moving on the graph. The calculator won’t tell you which function you’re tracing, nor will it tell you the coordinates of the cursor location.If you’ve graphed more than one function and you would like to trace a different function, press

Each time you press this key, the cursor jumps to another function. Eventually it jumps back to the original function.

**The values of**At the bottom of the screen, you see the values of the*x*and*y*:*x*- and*y*-coordinates that define the cursor location, provided the calculator is in**CoordOn**format. In the**PolarGC**format, the coordinates of this point display in polar form.When you press

**[TRACE]**, the cursor is placed on the graph at the point having an*x*-coordinate that is approximately midway between**Xmin**and**Xmax**. If the*y*-coordinate of the cursor location isn’t between**Ymin**and**Ymax**, then the cursor does not appear on the screen.Each time you press

the cursor moves right to the next plotted point on the graph, and the coordinates of that point are displayed at the bottom of the screen. If you press

the cursor moves left to the previously plotted point. And if you press

to trace a different function, the tracing of that function starts at the point on the graph that has the

*x*-coordinate displayed on-screen before you pressed this key.

Press **[CLEAR]** to terminate tracing the graph. This also removes the name of the function and the coordinates of the cursor from the screen.

When you’re using TRACE,** **if you want to start tracing your function at a specific value of the independent variable *x*, just key in that value and press **[ENTER]** when you’re finished. (The value you assign to *x* must be between **Xmin** and **Xmax**; if it’s not, you get an error message.) After you press **[ENTER]**, the trace cursor moves to the point on the graph having the *x*-coordinate you just entered.

If the name of the function and the values of *x* and *y* are interfering with your view of the graph when you use TRACE, increase the height of the screen by pressing **[WINDOW]**, and then decrease the value of **Ymin** and increase the value of **Ymax**.