# Émile Lemoine

**Émile Michel Hyacinthe Lemoine (22 November 1840 – 21 February 1912) was a French civil engineer and a mathematician. He is best known for his proof of the existence of the Lemoine point of a triangle. Other mathematical work includes a system he called Géométrographie and a method which related algebraic expressions to geometric objects.**

### About Émile Lemoine in brief

Émile Michel Hyacinthe Lemoine (22 November 1840 – 21 February 1912) was a French civil engineer and a mathematician. He is best known for his proof of the existence of the Lemoine point of a triangle. Other mathematical work includes a system he called Géométrographie and a method which related algebraic expressions to geometric objects. He has been called a co-founder of modern triangle geometry, as many of its characteristics are present in his work. For most of his life, Lemoine was a professor of mathematics at the École Polytechnique. In later years, he worked as a civil engineer in Paris, and he also took an amateur’s interest in music. Lemoine served in the French military for a time in the years following the publishing of his best-known papers. During his tenure as chief inspector of the gas supply of the city of Paris, he was responsible for the construction of the Paris Opera House. He died in Paris in 1912 and is buried in the Cimetière du Centre-Drouot in Paris. He was the son of a retired military captain who had participated in the campaigns of the First French Empire occurring after 1807.

His father had helped found the Prytanée of La Flèche, which Lemoine attended on a scholarship granted because his father had help found the school. As a student there, he helped to found an amateur musical group called La Trompette, for which Camille Saint-Saëns composed several pieces. In 1866, he considered a career in law, but was discouraged by the fact that his advocacy for republican ideology and liberal religious views clashed with the ideals of the incumbent government, the Second French Empire. He also lectured at various scientific institutions in Paris and taught as a private tutor for a period before accepting an appointment as a professor. In 1870, a laryngeal disease forced him to discontinue his teaching. He took a brief vacation in Grenoble and, when he returned to Paris, published some of his remaining mathematical research. During this early period, he published a journal article in Nouvelles annales de mathématiques, discussing properties of the triangle. He rose to the rank of chief inspector, a position he held until 1896.

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