Plato’s protractor investigations culminate in students using their windmill angle testers from early in the Explorer manual to understand the ability of the Mathomat protractor to measure in radians. The activities stop there, whereas of course there is a whole world of trigonometry-based exploration that can be explored using these concepts.
In their lesson plan Unwrapping the circle Susie Groves and Peter Grover present an explanation for using various elements within the Mathomat, including its unit circle, linear radian scale and protractor, to construct the sine curve. This includes an important discussion about the nature of pi, aimed at overcoming difficulties students often have with understanding pi simply as a number.
A future development of a Mathomat app is envisaged which shows how the various elements of Mathomat come together dynamically to measure distance trigonometrically. These can pull together the concepts in Plato’s protractor and unwrapping the circle so as to measure angle using Mathomat.
A future app for Mathomat is also interesting as a way of bringing Mathomat users closer to real angle contexts.
The Unwrapping the circle lesson can be downloaded free from this website, here. It can also be purchased as part of the teacher resource book Maths with Mathomat in the teaching resources section of this site.