Thematic+Unit

This lesson about the SSS Triangle Congruence Postulate fits into a unit in Geometry consisting of the various theorems and postulates that can be used to prove that two triangles are congruent. I would continue working with the students to propose what measurements we should ask the sorcerer Triangulo for as we worked through the other congruence postulates.

**Lesson Title:** Section 4.3: SSS Triangle Congruence Theorem
 * EALR’s:** G.1.B Use inductive reasoning to make conjectures, to test the plausibility of a geometric statement, and to help find a counterexample. G.3.B Determine and prove triangle congruence, triangle similarity, and other properties of triangles.
 * Objectives:** Students will be able to apply the SSS Triangle congruence theorem and create congruency statements.
 * Warm-up:** Review of yesterday’s activities (meeting Triangulo and finding triangle) and what it means for two triangles to be congruent.
 * Main task:** We will go through a discovery activity via a power point. Yesterday we met Triagulo a sorcerer who will grant us a wish if we have a triangle congruent to his. We found out yesterday that he will only give us three measurements of his triangle and so today we are going to try and figure out what measurements to ask for. Students will each get three metal fasteners and one bunch of three paper strips. They will construct a triangle and classify it by angles and/or sides. Then they will compare it to someone else’s triangle and record one similarity and one difference. They will the find the other student in the class who started with the same three strips (they are color coordinated by length) and compare their two triangles. They will decide if they are the same and if they can change them to make them different. Pairs with same triangles will then come up with a rule they think is always true (a.k.a. theorem) about triangles, sides, and congruence. They will be prepared to share their rule with the class. While they work on the activity I can informally assess their understanding by walking around observing their progress. I will observe pairs’ rules and select interesting/valuable ones to be presented to the rest of the class. After students have shared their theorems I will tell them the official theorem from their book.


 * Closure:** Given the theorem we have discovered I will ask students what information we should ask Triangulo for, then we will find out he will only give us one side!! Then what? We’ll find out in the next lesson.