Thales of Miletus

The empirical geometry of Egyptians reached the ancient Greek through commerce, travel, and warfare. One of the first Greek scholars to study this geometry was Thales of Miletus. Thales is known as the first of the Seven Sages of Greece.

A successful businessman, statesman, and philosopher, Thales had occasion to travel to Egypt and consequently learned of Egyptian geometry. While in Egypt, he won the respect of the pharaoh by calculating the height of the Great Pyramid of Cheops. He did this by measuring the shadows of the pyramid and of his walking staff. Knowing the height of his staff, he used a proportion to calculate the height of the pyramid.



In history of mathematics, Thales is credited with being the first to prove that corresponding sides of similar triangle are proportional. If the three angles of one triangle are equal to the three angles of another triangle, the triangles are similar. Consequently, similar triangle have the same shape but may differ in size.

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