ATRACTOR

With the following app, you can draw several geometric figures in the plane and manipulate them in various ways, by changing the colour and size, rotating them or dragging them. Simultaneously, the app shows the inversions with respect to a circle, allowing thereby the observation of some interesting properties related to these transformations. If you do not have any knowledge about what inversion is, before using this app, we advise you to first read a short introductory course. Many difficult problems in geometry become more tractable when an inversion is applied.

Click on the image to access the app about inversion

(*) This work was carried out under a grant by FCT - Fundação para a Ciência e a Tecnologia.
Since many browsers are blocking Java nowadays, it was decided (in 2022) to convert to Javascript the original applet of this section. This conversion was carried out by a high-school teacher, who is working full-time in Atractor with the support of the Ministry of Education.