In this clip the discussion turns to how things would change if their circle had a different radius.
Worksheet 2, Clip 1, Discussion of Circumference, 1:32
The students realize they are looking for a distance, but the teacher wants to ensure they are all looking for the same distance. Notice how he continues the conversation until they are talking about it using the language of the classroom
One student mentions the radius and tangent line. The teacher does a good job in havnig this student make his thinking obvious.
He also uses the student's construction to ask his questions about the worksheet
Finally he does use the term circumference in referring to the distance around the circle. It is important that the terminolgy be used often so the students will form a common way of talking about trigonometry.
