III. Working With A Graph
F. TRACE
TRACE is a very useful tool in graph analyses. Even when a graph is not visible, you can use TRACE to find yvalues. When using TRACE, the xvalues are restricted to the interval [xMin, xMax]. For values outside of that interval you will have to change the window or use TABLE. However, the yvalues are not restricted to [yMin,yMax].
If you try to enter a value outside of the interval [xMin, xMax], you will get an error message as shown below. However, if you just use the cursor to TRACE, the graph will be redrawn as you move out of the set WINDOW.
Example 1: Graph the function shown and use ZDECM as the window. Note what happens when you enter the value x=2 where the function is not defined.
Enter the
function. 
Set a ZDECM
window. 
Access TRACE.

Enter the
value x=2. 
Enter the
value x=2. 
Use the TRACE
key to trace to x=7. 
Enter the value
x=10. 
You will see
this message. 
Example 2: In this example, the yvalues are so small that the graph does not show on the screen. However, the TRACE key can still be used to find Yvalues.
Enter the function. Use ZDECM
to graph. Access TRACE;
enter x=1.ZDECM is called a friendly window because TRACE moves in increments of x=0.1. For other windows, the TRACE will most likely not move to a value you want, so you can just enter the xvalue you desire.