Ptolemy

Ptolemy was a Greek mathematician and astronomer who lived around 100 AD. He is best known for his work in geometry and astronomy, especially the "Almagest," which detailed the geocentric (Earth-centered) model of the universe. In geometry, he developed the Ptolemaic theorem, which describes a relationship in cyclic quadrilaterals—shapes with four corners where all vertices lie on a circle. This theorem is foundational in understanding angles and distances in various geometric contexts, influencing both mathematics and navigation for centuries. Ptolemy's ideas shaped how we perceive space and celestial movements.