A Machine-Checked Direct Proof of the Steiner-Lehmus Theorem
summary
States a direct constructive proof of the Steiner–Lehmus theorem that is fully machine-checked inside a constructive proof assistant, avoids the law of excluded middle, and grounds geometry on a new set of constructive axioms with constructive reals. Formalization derives 28 of the 48 propositions from Book I and assembles roughly about 1500 proof objects, builds a parallelogram and case splits on stable conclusions, and runs entirely inside the New Pearl environment so no classical hidden steps remain.
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