Hey Avery,

When I first quizzed the first group of students, it was with the original sketch on my own computer. I just asked them to tell me when they wanted me to stop the purple region from growing. I then manually entered the results into the spreadsheet view and displayed the list of points. With the geometry students they all ran the sketch on their computer and then shouted out their numbers. It would be just as easy (I imagine) to have a group of people in a todaysmeet.com and enter their answers. A student volunteer could then enter the values into a spreadsheet that automatically plots the points.

After getting a comment similar to yours about the angle from another person during school, I changed the number to showing percentage instead of angle – it absolutely made a big difference. At the time I chose to display the angle, it was for ease of gathering data. The sketch wasn’t really an interactive activity that would be used for an individual student to really explore the concept. In the later version I posted at http://bit.ly/rDARUH it is meant for students to explore a bit more, and that includes the percentage of purple rather than the angle.

Thanks for the comments – I love arbitrarily assigning myself Geogebra challenges. Dan tends to be a great source of those….

and a comment…
Instead of describing the angle you stopped at, I might describe the ratio of the circumference you stopped at since (I think) this more easily leads to the idea of weighted averages.