• DOI:10.1145/3497775.3503682
• Corpus ID: 245353427

A machine-checked direct proof of the Steiner-lehmus theorem

@article{Kellison2021AMD,
  title={A machine-checked direct proof of the Steiner-lehmus theorem},
  author={Ariel E. Kellison},
  journal={Proceedings of the 11th ACM SIGPLAN International Conference on Certified Programs and Proofs},
  year={2021}
}

• Ariel E. Kellison
• Published 18 December 2021
• Mathematics
• Proceedings of the 11th ACM SIGPLAN International Conference on Certified Programs and Proofs

A direct proof of the Steiner-Lehmus theorem has eluded geometers for over 170 years. The challenge has been that a proof is only considered direct if it does not rely on reductio ad absurdum. Thus, any proof that claims to be direct must show, going back to the axioms, that all of the auxiliary theorems used are also proved directly. In this paper, we give a proof of the Steiner-Lehmus theorem that is guaranteed to be direct. The evidence for this claim is derived from our methodology: we have formalized a constructive axiom set for Euclidean plane geometry in a proof assistant that implements a constructive logic and have built the proof of the Steiner-Lehmus theorem on this constructive foundation.