Introducing Tactic and Discussing Goals

In this session, we spent time going through the lean_lec_feb9.lean file in the lean_lectures folder of the Github repository. In particular, we reviewed tactics found in the Natural Numbers Game, stepped through a proof that the sum of the first n odd natural numbers is equal to n^2, and live coded a proof of FiniteField.prod_univ_units_id_eq_neg_one, including demonstrating the refine tactic.

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Date published: Monday, February 9, 2026