It is not clear at the outset in dynamic geometry how the buttons relate to each other, or that the possibility of catastrophic circularity can be avoided. This was something previous writes such as Euclid were at pains to avoid. Hence we ask "how does this button work?". Or, put another way, this article is one attempt to examine the dynamic geometry package GeoGebra from the point of view of Euclidean Constructions.
Published August, 2007; article ID 1606. Copyright © 2007, Christopher J. Sangwin