An Application of CLP: Checking the Correctness of Theoremsin Geometry

  • Authors:
  • Denis Bouhineau;Laurent Trilling;Jacques Cohen

  • Affiliations:
  • IRIN, University of Nantes, France;LSR-IMAG University of Grenoble, France;Brandeis University, Waltham, Massachusetts, USA

  • Venue:
  • Constraints
  • Year:
  • 1999

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Abstract

ConstraintLogic Programming can be advantageously used to deal with quadraticconstraints stemming from the verification of planar geometrytheorems. A hybrid symbolic-numeric representation involvingradicals and multiple precision rationals is used to denote theresults of quadratic equations. A unification-like algorithmtests for the equality of two expressions using that representation.The proposed approach also utilizes geometric transformationsto reduce the number of quadratic equations defining geometricconstructions involving circles and straight lines. A large number(512) of geometry theorems has been verified using the proposedapproach. Those theorems had been proven correct using a significantmore complex (exponential) approach in a treatise authored byChou in 1988. Even though the proposed approach is based on verification—ratherthan strict correctness utilized by Chou—the efficiencyattained is polynomial thus making the approach useful in classroomsituations where a construction attempted by student has to bequickly validated or refuted.