Euclid

EUCLID
(c. 330 – 275 BC)

A mathematician of Alexandria, Euclid is the person whose name is most closely associated with geometry among all mathematicians who have ever lived. He owes this distinguished place less to being a great original mathematician than to having collected everything known about geometry, from its beginnings up to his own time, in his book the Elements. The Elements has been translated into many languages, copied hundreds of times and, after the invention of the printing press, revised thousands of times. To make his compilation a consistent whole, Euclid set out five axioms, self-evident truths that require no proof, and derived all other propositions from them.

These are:

  1. Exactly one straight line passes through any two points.
  2. A line segment can be extended indefinitely in both directions.
  3. A circle can be drawn given its center and a point on it.
  4. All right angles are equal.
  5. Through a point not on a given line, exactly one line parallel to it can be drawn.

The Elements consists of 13 books:

  • I: Congruence, parallels, the Pythagorean theorem
  • II: Identities, area calculation, the golden ratio
  • III: Circles
  • IV: Polygons inscribed in and circumscribed about circles
  • V: The theory of ratio and proportion
  • VI: Similarity of polygons
  • VII, VIII and IX: Arithmetic and early number theory
  • X: Incommensurable magnitudes
  • XI, XII and XIII: Solid geometry

Euclidean geometry remained unrivaled until the beginning of the 19th century. Even until the mid-20th century, geometry in secondary schools was taught based on Euclid’s Elements.

Almost nothing is known about Euclid’s life. It was once believed that he was born in Megara, a Greek city, but it later turned out that Euclid of Megara was a philosopher who lived about a century before Euclid of Alexandria, the author of the Elements.

Works:

  1. Elements (the basis of what came to be called Euclidean or elementary geometry)
  2. Data (Dedomena)
  3. Surface Loci
  4. Optics (Optica)
  5. Porisms