Education Technology

Get to the Point! Coordinate Geometry!

Published on 06/09/2008

Activity Overview

In this activity, students use the Geoboard to determine the area of any polygon using coordinates.

Before the Activity

  • Start the Geoboard App and format it
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 113 - 118 from the attached PDF file for your class
  • During the Activity

    Distribute the page to the class.

    Follow the Activity procedures:

  • Construct a heptagon using the coordinates of its vertices
  • Starting at any point and moving counterclockwise around the polygon, list the vertices in a vertical column in consecutive order
  • Repeat the starting point at the bottom of the list
  • Calculate D, the sum of the down diagonal products, and U, the sum of the up diagonal products
  • Determine the area of the polygon which is one-half of the difference between D and U

  • Construct a square, draw a diagonal, and a line segment that divides the square into four non overlapping regions
  • Find the ratios of the areas of the four regions
  • After the Activity

    Students complete the Activity sheet and answer questions.

    Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary