Pappus of Alexandria

Teaching mathematics in Roman Alexandria in the early 4th century CE, Pappus recognized that the geometric wisdom of earlier Hellenistic polymaths was at risk of extinction. He compiled the *Synagoge* (Mathematical Collection), a comprehensive eight-volume synthesis of geometric proofs, mechanical inventions, and astronomical calculations.

He formulated *Pappus's hexagon theorem*—the foundation of modern projective geometry—as well as the *Pappus-Guldinus centroid theorems* used in calculus for calculating volumes of solids of revolution. His commentaries preserved works of Apollonius, Euclid, and Archimedes that would otherwise have been lost to humanity.