Education Technology

Looks Right

Activity Overview

Students use the Cabri Geometry II Plus software to determine which given triangle retains its basic shape after its vertices are dragged around the screen.

Before the Activity

  • Download the Cabri Geometry™ software on the computer
  • See the attached FIG file for details of this activity

  • During the Activity

    Follow the Activity procedure:

  • Drag the vertices of the first triangle (figure A) around the screen
  • Observe that along with the angles, the shape also changes
  • Drag the vertices of the second triangle (figure B) around the screen
  • Notice that the size of the triangle changes, but segment GD is always perpendicular to segment DE
  • After the Activity

    Review student results:

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