Mr. Stephenson's Compilation of Math History

Ancient Babylon & Egypt (~3500 BC - 2000 BC)

Geometry comes from greek words meaning to measure land. Its basic principles were developed in Babylonia and Egypt to measure farmers' lands after the annual river floods for accurate taxation. It also served well in other pursuits, like building pyramids.

Pythagoras (569 BC - 475 BC)

He probably was the first to prove the "Pythagorean Theorem", but the principle was known 1000 years earlier in Babylonia. His cult-like school discovered irrational numbers like the square root of 2, but they tried to keep the knowledge secret because it didn't fit with their philosophy/religion about numbers.

Theaetetus (417 BC - 369 BC) - [see Euclid below]

Eudoxus (408 BC - 355 BC) - [see Euclid below]

Plato (427 BC - 347 BC)

In Athens about 387 BC Plato founded, on land which had belonged to Academos, a school of learning which, being situated in the grove of Academos, was called the Academy (hence our english word). Over the door of the Academy was written (in ancient greek, but translated here):

Let no one unversed in geometry enter here.

Euclid of Alexandria (325 BC - 265 BC)

Euclid wrote The Elements, a compilation of knowledge that was the primary source for the teaching and learning of mathematics for 2000 years.

It is sometimes said that, next to the Bible, The Elements may be the most translated, published, and studied of all the books produced in the Western world. … The Elements must make [Euclid] the leading mathematics teacher of … all time.

The 13 books of The Elements contain:

Books 1-6: plane geometry (based on works of Pythagoras and Eudoxus);

Books 7-9: number theory (incl. greatest common divisors and geometrical progressions);

Book 10: theory of irrational numbers (mainly works of Theaetetus and Eudoxus); and

Books 11-13: three-dimensional geometry (mainly works of Theaetetus and Eudoxus).

Plane geometry is also known as Euclidian geometry.