Education Technology

Coordinate Geometry - Circles

Published on 06/09/2008

Activity Overview

In this activity, students investigate the relationship between the coordinates of a point on the circle, radius of a circle, and the values in the equation of the circle.

Before the Activity

Install the Cabri® Jr. App on the students' graphing calculators using one of these two methods:

  • TI-Connect™,  a TI Connectivity Cable, and the Unit-to-Unit Link Cable
  • TI-Navigator™  "send to class" feature
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 1 - 10 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the Activity procedures:

  • Draw a circle of any radius in quadrant 1
  • Drag the circle so that the center of the circle is at the origin
  • Display the coordinates of point P, where the circle intersects the x-axis
  • Display the coordinates of the center and the equation of the circle
  • Notice that the x-value of P represents the radius of the circle
  • Drag point P along the x-axis and relate the equation of the circle to the coordinates of point P
  • Move the center of the circle away from the origin
  • Observe the coordinates of the center and point P
  • Observe how the values relate to the equation of the circle
  • After the Activity

    Review student results:

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