In about 2,500 BC the abacus came into use by the Babylonians in Mesopotamia, today's Iraq. The Vedic people from this same region less than 100 kilometres south of Baghdad, entered India about 1500 BC. They wrote texts known as Vedas, which date between the 15th and the 5th century BC. Later the Indian Sulbasutras texts were added, becoming appendices to the Vedas, and these set out rules for the construction of altars for religious worship. The most important of these appendices are the Baudhayana Sulbasutra, written around 800 BC and the Apastamba Sulbasutra written around 600 BC. Certain of the calculus contained within the Sulbasutras demonstrate the principle of Pythagoras' theorem. In the Baudhayana Sulbasutra a special case of the theorem is written explicitly:- "The rope which is stretched across the diagonal of a square produces an area double the size of the original square." The Katyayana Sulbasutra gives a more general version:- "The rope which is stretched along the length of the diagonal of a rectangle produces an area which the vertical and horizontal sides make together." As these texts attest, although known some 1,000 years before Pythagoras' time, he is credited with being the first mathematician to actually prove the theorem which was much later named after him. A portion of a 4000 year old Babylonian tablet (c. 1900 B.C.E.), now known as Plimpton 322, (in the collection of Columbia University, New York), lists columns of numbers showing what we now call Pythagorean Triples - sets of numbers that satisfy the equation. It is also known that the Egyptians used a knotted rope as an aid to establish right angles in the construction of their buildings. The rope had 12 evenly spaced knots, which could be formed into a 3-4-5 right triangle, thus giving an angle of exactly 90 degrees.

Most historians agree that Pythagoras travelled to Phoenicia, (modern-day Lebanon) and also to Babylon in Mesopotamia with his father, who was a merchant. As an adult Pythagoras went to Egypt to study, so it can be assumed that he studied the above knowledge of these civilizations. However, modern research throws considerable doubt upon the many discoveries attributed to Pythagoras, as discussed on this website of Stanford University : http://plato.stanford.edu/entries/pythagoras/ .

Thales (b. approx. 624 BC in Miletos, Asia Minor - now Turkey - and died about 546 BC in Miletos), was the first known and recorded Greek philosopher, scientist and mathematician. He brought Babylonian mathematical knowledge to Greece and if not a tutor to Pythagoras, he certainly advised and influenced him and is said to have encouraged Pythagoras to travel and learn from the "Chaldeans", otherwise known as the Babylonians.

Quoting Wikipedia Encylopedia: "We find mentioned as his instructors Creophylus,[11] Hermodamas,[12] Bias,[13] Thales,[14] Anaximander,[15] and Pherecydes of Syros.[16] The Egyptians are said to have taught him geometry, the Phoenicians arithmetic, the Chaldeans astronomy, the Magians the formulae of religion and practical maxims for the conduct of life.[17] Of the various claims regarding his Greek teachers, Pherecydes is the most oft-mentioned figure."