This time is used for the students to refresh their memories of the work completed the day before on Triangle Diagrams. I ask the students to look over and discuss in their group their work from the previous lesson, so that we can begin to discuss the conclusions they have reached with the entire class.
Now, the discussion phase of this lesson starts! Beginning with the first problem in Triangle Diagrams, I choose a number from 1 to 4, and ask each student in the groups with this number to briefly explain his/her group’s findings on that problem. As students offer explanations I highlight different approaches, should they occur, and bring up for discussion among the students any uncertainty or potential misconceptions in students’ reasoning.
I then move on to the next diagram, choosing another number from 1 to 4, asking students with this number to present, and continue in this fashion, through item 8. With regard to these problems, here are some preliminary expectations based on my experiences with the lessons:
(See Discussion Notes Narrative Full for a slightly more detailed presentation.)
Similar to the first part of this lesson, delivered the day before, I ask the students to return their attention to the board on which they have listed ways of proving angles congruent when working with similar triangles. I ask several questions to summarize the investigation and followup discussion:
As the students leave the class, I hand out Similar Triangles Homework Proof. This proof recalls the work done on similar triangle proofs previously, and in particular applies the work that students did in this lesson.