Pixels and Step Size on the TI-85: A Technical Exercise

By Gary A. Harris
Department of Mathematics
Texas Tech University
Lubbock, Texas 79409
g.harris@ttu.edu

Introduction

It is important for people using graphing calculators to understand how their calculator samples the variable x, and how this sampling depends on the number of horizontal pixels on the screen, and the minimum and maximum values of x. This is especially important for students who expect to be using this technology to teach mathematics. Not only will they need to be able to explain strange pictures occurring because of inappropriate range settings for x, but they will also need to be able to choose appropriate range settings so as to exhibit phenomenon that is associated with a particular value of x, hence requiring this value of x to be a sample point. This exercise (available in the following formats: PDF, WordPerfect, PS) is intended to provide the students with that understanding.

The exercise is written for the TI-85, but should be easily revisable to accommodate any graphing calculator. Students might find it interesting that the exercise concludes with a few exercises involving the greatest common divisor of two integers.