Early study of trigonometry began with the ancient Egyptians and Babylonians studying properties of triangles in the 2nd millennium BC. This study continued and advanced in Hellenistic Greece and India, where systematic study of trigonometric functions began. During the Middle Ages, Islamic mathematicians adopted trigonometry as a separate subject and it spread to Western Europe in the Renaissance. Modern trigonometry developed further during the 17th-18th centuries with key contributions from mathematicians like Newton, Stirling, and Euler.