In this clip the teacher involves the students in a discussion about what happens with the angle measure if the radius of the circle is increased.
Protractor Applet, Clip 2, Moving Ray, 3:28
Before actually moving the ray he has the students make conjectures about what they expect to happen.The students are asked to focus on which calculations will change and which will remain the same.
The teacher uses questioning in order to focus students on the dynamic changes in angle measure as he moves the ray.
He asks about how the arclength changes.
He asks about how the circumference changes.
He asks about the measure of the angle.
This is a good way to keep the students involved in their learning.
Notice how the teacher involves as many students as possible.
After they make their conjectures, the teacher moves the ray and asks the students to determine if they got what they expected. He even stops at 90 degrees to ask about a couple of the calculations.
He is also reinforcing the terminology that is to be used by reminding them they are dealing with the circumference of the circle (as opposed to the circle as an object).
