Sridharacharya was an Indian mathematician from the 9th century AD who made several important contributions to geometry. He wrote two major mathematical treatises called Patiganita and Trisatika that covered topics like arithmetic, algebra, geometry, and the early concepts of calculus. In these works, Sridharacharya provided early formulas for the volumes of spheres and segments of circles. He also explicitly defined the rules of zero for the first time, such as how it affects addition, subtraction, multiplication and division.