Education Technology

Algebra 1: Horizontal and Vertical Lines
by Texas Instruments

Published on December 01, 2011


  • Students will identify lines with zero and undefined slope.
  • Students will describe, in terms of coordinates, what is special about points on horizontal and vertical lines.
  • Students will explain why the slope of a horizontal line is zero and why the slope of a vertical line is undefined.


  • Slope

About the Lesson

The activity involves examining the vertical and horizontal changes when moving from one point to another on a line. As a result, students will:

  • Understand that when the vertical change between two points is zero, the slope is zero, and when the horizontal change between two points is zero, the slope is undefined.
  • Move points and will observe the line move as well as the vertical and horizontal change.