

Objective:
This graphing calculator based demo illustrates that conclusions we make
about the domain and/or range of a function using the graph only may not
be accurate. Because of limitations in how the calculator plots
points in the function mode, it is important to make an analytic
investigation of domain PRIOR to interpreting a calculatorgenerated
graph.
Level: This demo is appropriate College Algebra, Precalculus, or any course in which graphing calculators are used for graphing functions. Prerequisites: Students should have basic graphing calculator skills. In the examples, a TI85 was used to produce the graphs. (Results are similar when using a TI83 or TI89.) Equipment: You will need a graphing calculator and either a display device for the calculator or screen capture utility so that calculator graphics may be printed to a transparency. Example 1: Plot the graph of and give the domain.
Using the graph and the trace feature on the calculator to estimate the domain, it appears that the domain does not include values of x close to 3. Demonstrate that an analytic examination of the function
shows that the domain is [3,Infinity).
A look at the table generated by the function using the table settings below indicate that the calculator is computing the function values correctly: the points are just not being plotted on the graph. The ERRORs occur outside the domain of the function. Example 2:
Reference
Credits: This demo was submitted by
and is included in Demos with Positive Impact with her permission.


Created 12/21/1999 LFR.
Last updated 9/15/2010 DRH. Visitors since 2/2/2005
