With the following applet, 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 applet 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 applet, we advise you to first read a short introductory course. Many difficult problems in geometry become more tractable when an inversion is applied.
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(*) This work was carried out under a grant by FCT - Fundação para a Ciência e a Tecnologia.
Difficulty level: University