♦♦♦ Anti-associativité

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A symmetry appearing out of nowhere, an equilateral triangle emerging amid the trisectors of a completely arbitrary triangle: that is the whole "miracle" of Morley and his theorem. The many proofs of this beautiful property are marvels of geometry and trigonometry.

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In this bicentenary year of 2021, let's revisit a result that bears his name. The emperor is said to have had a keen interest in geometry; according to one story, he once discussed the subject with two mathematicians of his day, Joseph Lagrange (1763–1813) and Pierre-Simon Laplace (1749–1827).