Euclid

Euclid (Ancient Greek: Εὐκλείδης – Eukleídēs), sometimes given the epithet Euclid of Alexandria, was a Greek mathematician, often referred to as the "father of geometry". He was active in Alexandria during the reign of Ptolemy I (323–283 BC).

His Elements is one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematics (especially geometry) from its publication until the late 19th or early 20th century. In the Elements, Euclid deduced the principles of what is now called Euclidean geometry from a small set of axioms. Euclid also wrote works on perspective, conic sections, spherical geometry, number theory, and rigor.

Little is known about Euclid's life. He is primarily known through references in the writings of Proclus and Pappus of Alexandria, several centuries later. Proclus believed that Euclid belonged to Plato's school. Pappus mentions Euclid in connection with Apollonius of Perga. The Elements consists of thirteen books, covering plane geometry, number theory, solid geometry, and the method of exhaustion.

Beyond the Elements, Euclid is credited with several other works, including:

• Data: A collection of geometrical theorems concerning the nature of given elements in geometrical figures.
• On Divisions of Figures: A work concerning the division of geometrical figures into parts having specified ratios. Only fragments survive.
• Optics: The earliest surviving Greek treatise on perspective.
• Phaenomena: A treatise on spherical astronomy.
• Surface Loci: A collection of theorems concerning loci, which are sets of points that satisfy certain conditions. This work is lost.