What Is a Line ?
The playground is the projective complex plane. The article shows that usual, naive, lines are not all lines. From naive lines (level 0), Pappus geometry creates new geometric objects (circles or conics) which can also be considered as (level 1) lines, in the sense that they fulfil Pappus axioms for lines. But Pappus theory also applies to these new lines. A formalization of Pappus geometry should enable to automatize these generalizations of lines.
KeywordsIntersection Point Common Point Generalize Line Common Line Dynamic Geometry Software
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