Download Similar Triangles on the Coordinate Plane (SSS Theorem by

Project AMP
Dr. Antonio Quesada – Director, Project AMP
Similar Triangles on the Coordinate Plane
(SSS Theorem by Construction)
Lesson Summary:
Students will construct two similar triangles using Geometry software and
discover the Side-Side-Side Similarity Theorem
Key Words:
similar triangles, SSS Similarity Theorem
Background Knowledge:
Students should be familiar with the Geometry software.
Learning Objectives:
Students will discover the SSS Similarity Theorem and use it to prove that two
triangles are similar.
Materials:
Geometry software
Suggested Procedure:
Split students into groups of two or three. Have students complete the
worksheets.
Project AMP
Dr. Antonio Quesada – Director, Project AMP
Similar Triangles on the Coordinate Plane
(SSS Theorem by Construction)
Group member’s names: __________________________________________________
File name: _____________________________________________________________
Goal: Construct two similar triangles on the coordinate plane and determine the
relationship of the angles and sides of these triangles.
Perform the following tasks using Cabri*:
1. Show the coordinate plane on your screen. [Use show axes and define grid tools]
2. Construct three points A, B, and C. Put point A at (-1,1), point B at (2,1) and
point C at (0,-2) and label each point. [Use the point and label tools]
3. Construct the segments AB , BC , and CA . [Use segment tool]
4. Construct three points D, E, and F. Put point D at (-3,3), point E at (6,3) and
point F at (0,-6) and label each of these points. [Use the point and label tools]
5. Construct the segments DE , EF , and FD . [Use segment tool]
6. Find the length of all the segments. [Use distance and length tool]
7. Calculate the ratio of AB to DE , BC to EF , and CA to FD . Put these ratios
in a blank section of your screen and use the comment tool to rename each for
clarity. [Use calculate and comment tools]
8. What did you find out about the ratios of the sides of these two triangles?
9. Find the measurements of all the angles in ∆ ABC and ∆ DEF. [Use the angle tool]
10. How are the measurements of ∠ BAC and ∠ EDF related? How about ∠ ABC
and ∠ DEF? ∠ BCA and ∠ EFD?
11. What can you conclude about these two triangles? Explain how you came to your
conclusion.
If you are not familiar with Cabri’s tools, press F1. A help menu for each tool selected will appear on the screen.
Project AMP
Dr. Antonio Quesada – Director, Project AMP
Similar Triangles on the Coordinate Plane
(SSS Theorem by Construction)
1. What was your favorite thing about this activity?
2. What was the most challenging thing?
3. What did you gain the most confidence about through completing this
lesson?
4. Where do you possibly see yourself using this knowledge in the future?