Euclid, sometimes called Euclid of Alexandria to distinguish him from Euclid of Megara, was a Greek mathematician, often referred to as the "father of geometry". He was active in Alexandria during the reign of Ptolemy I. His Elements is one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematicsfrom the time of its publication until the late 19th or early 20th century. In the Elements, Euclid deduced the principles of what is...
(wikipedia)