Dionis
# Achille Pierre Dionis du Séjour

### Born: 11 Jan 1734
in Paris, France

Died: 22 Aug 1794
in Vernou (near Fontainebleau), France

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**Dionis du Séjour** published a treatise on the analytic geometry of plane curves in 1756 and wrote extensively on applications of mathematics to astronomy, in particular planetary orbits. He also worked on the theory of equations, not attaining the depth of results of Bézout or Lagrange. With Condorcet and Laplace he undertook a determination of the population of France.
**References (2 books/articles)**

JOC/EFR December 1996