Trigonometry is the part of geometry that studies the relationships between the lengths of the sides of a triangle and the size of its angles. (The Greek word TRIGONO + METRY means "triangle measurement".) All ancient Mediterranean peoples, particularly the Babylonians, had a hand in developing trigonometry -- they wanted to get an accurate map of the stars and planets in the heavens, and to solve practical geometry problems on earth. Between 300 BC and 200 AD the Greeks organized the subject and developed most of what we today call trigonometry. It was Ptolemy, the Greek astronomer who worked in Egypt in the second century AD, who produced a text book that served as the standard for the next 1700 years.