This lesson takes place in an eighth grade algebra classroom of approximately 30 students in the spring, in a suburban school in Southern California. Cindy, the teacher, uses the Triangles task as the class is finishing up a unit on linear functions. We drop in after students have worked on the problem and the teacher is pulling them back for a whole group discussion.

The lesson graph depicts the mathematical flow of the lesson and is divided into lesson elements. The length of time for each of these lesson elements is noted in the far left column. As you review the lesson graph:

Note the teal highlighted portion that represents where the clip is situated in the lesson.
Make note of the various lesson elements (launch, explore, summarize) and their relative lengths of time.
Look at what happens before and after the clip to get a sense of the lesson as a whole. In particular, take note of how Cindy summarizes the triangles discussion after the clip.

You can view the lesson graph below (or click the arrow to download a PDF version).