Included: Flipchart, Sentence strips to cut and sort, Notes handout
This is the lesson I used to introduce the idea of Triangle Congruence Proofs. I used this for classes with on-level students and special education students as well as my self-contained ESOL geometry students. It is low-level, but worked well as a simple introduction. Because of my level of students I am very cautious about the language I use and how I present it. Whenever possible I simplify and use visuals opposed to wordy definitions.
My main approach to triangle congruence proofs is "telling a story."
I started with showing them a story about a girl that was all jumbled and out of order. They were given the sentence strips to sort and put in order. I then asked questions about the story in which they had to explain/justify why the girl was able to do certain things.
I then gave them a simple story about two triangles that had matching parts. Again, the story was jumbled and they had to put it in order. I asked why from the story the triangles were congruent. The conclusion was SAS.
So then I was off!
I told them they were detectives in geometry and they just wrote their first geometry proof, but didn't know it! We had a small class discussion about what the word proof means in both English and Spanish.
I always tell my students that we are just telling a story: "There once was two triangles.... and they were congruent. But we need the evidence for our story!" Our stories then can look like paragraphs (which I do not emphasize), two-columns, or flowcharts. No matter how the story is written it needs the evidence about your triangles!