Theorems on regular polygons

Watkins and Zeitlin (1993) published a method to simply compute the minimal polynomial of cos(2π/n), based on the Chebyshev polynomials of the first kind. By using their method GeoGebra is able to prove various properties of regular n-gons since November 2017. This collection demonstrates how useful this new feature is. As a further improvement of the Watkins-Zeitlin method, another software tool RegularNGons can be used to automatically find interesting features of a regular polygon.