Formalizing Desargues' theorem in Coq using ranks in Coq
Abstract
Formalizing geometry theorems in a proof assistant like Coq is challenging. As emphasized in the literature, the non-degeneracy conditions leads to technical proofs. In addition, when considering higher-dimensions, the amount of incidence relations (e.g. point-line, point-plane, line-plane) induce numerous technical lemmas. In this paper, we present an original approach based on the notion of rank which allows to describe incidence and non-incidence relations such as equality, collinearity and coplanarity homogeneously. It allows to carry out proofs in a more systematic way. To validate this approach, we formalize in Coq (using only ranks) one of the fundamental theorems of the projective space, namely Desargues' theorem.
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