Education Technology

Angle Theorem

Published on 06/09/2008

Activity Overview

Students use the Cabri Geometry II Plus software to investigate the relationship between angle and ratio in a right triangle.

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:

  • Select the multiple animation option from the toolbar
  • Animate the number 40 [the angle] and observe the effect on the length of sides and ratio of the side lengths
  • Note that as the angle increases, the length of base decreases, the height increases, while the hypotenuse retains its length
  • Observe that as the angle increases, the ratio of the opposite side to the hypotenuse increases, and the ratio of the adjacent side to the hypotenuse decreases
  • Recognize the fact that sin 90° = 1
  • After the Activity

    Review student results:

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