This lesson is for teachers to use technology to invoke a thoughtful and engaging classroom experience with their students. It is designed to show concretely through Geogebra all of the triangle congruences and all of the combinations that don’t work. This is a fantastic way for a teacher to show this to their students because it is difficult on a white board or with pen and paper to prove to the students that these congruences work. The most insightful part of this lesson is where the combinations that don’t work are shown to the students and the students can see on the screen why.

Geogebra is an excellent source that teachers can use which can incorporate visual understanding of many geometry lessons. It is a completely free computer application which can be downloaded here: https://www.geogebra.org/download. This application specifically allows a person to manipulate different points, lines, angles, and other things in ways that a pencil and paper cannot. For this lesson specifically, it works fantastically because of the free motion that the program gives you.

Common Core State Standard:

HSG.CO.B.8: Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions.

Lesson plan: technology-lesson-plan_triangle-congruencies

Attached worksheet: http://cdn.kutasoftware.com/Worksheets/Geo/4-SSS%20SAS%20ASA%20and%20AAS%20Congruence.pdf