Euclid. Engraving of Euclid (flourished about 300 BC), Greek mathematician. Working in Alexandria (now in Egypt), Euclid brought together previous work in mathematics and his own results. He recorded these in a systematic way in thirteen books called Elements of Geometry. Six books deal with the geometry of planes, four with the theory of numbers and three with the geometry of solid objects. Euclid's work was translated into many different languages and dominated mathematics for over 2000 years. The Elements were the first mathematics books to be printed. Errors were not found in Euclid's work until the 19th century; most of his findings remain valid.