Students can start to study area of circle by first discussing ways to estimate their area. They can see by inscribing regular polygons with more sides a better estimate is given. From the previous lesson, students found the area of various regular polygons. This can be used to find the estimates. Click here for a GSP Sketch.
Exact area of circles should be found as well. Students need to understand circumference for this part of the lesson (from Lesson 3). One way to find the area of a circle involves slicing the circle into small pieces. Then, rearrange them to look more like a rectangle, a shape that has an area we know. Click here for a GSP 3.0 sketch of this idea. A short clip on the video The Story of Pi presents a great visualization as well.