Although in some cases, students were eager to continue to gather data to justify thinking, when prompted by other students or the teacher, they began to make general observations about angles and triangles to support their arguments.

The students show how well they understand what is to be proven by how they organize their approach. Some students are better able to self-assess whether the path they are taking is useful. They used phrases like "getting close," which shows not only their growing understanding of reasoning, but also that they have a concept of what the proof that angle C is a right angle would look like.