Indian mathematician Aryabhata made several important contributions to mathematics in the 5th century CE, including developing a place-value system, trigonometric functions, and approximations of pi. He wrote the Aryabhatiya, which covered topics such as algebra, arithmetic, plane trigonometry, and spherical trigonometry. Some of his key contributions were developing a place-value numeral system, approximating pi as 3.1416, and calculating sine tables and trigonometric formulas. He is considered one of the greatest mathematicians of ancient India.