Vatasseri Paramesvara (1380–1460) was a mathematician and astronomer of the Kerala school of astronomy and mathematics. He proposed several corrections to the astronomical parameters which had been in use since the times of Aryabhatta! He was a genius of observational astronomy and spent more than 55 years of his life just observing happenings in the sky.
Paramesvara was a proponent of observational astronomy in medieval India and he himself had made a series of eclipse observations to verify the accuracy of the computational methods then in use. The computational scheme based on the revised set of parameters has come to be known as the Drgganita system. Paramesvara was also a prolific writer on matters relating to astronomy. At least 25 manuscripts have been identified as being authored by Paramesvara.
Parameshvara wrote commentaries on many mathematical and astronomical works such as those by Bhaskara I and Aryabhatta. He made a series of eclipse observations over a 55 year period, and constantly attempted to compare these with the theoretically computed positions of the planets. He revised planetary parameters based on his observations.
Paramesvara’s most significant contribution in Mathematics is his mean value type formula for inverse interpolation of sine. He is the first mathematician to give the radius of circle with inscribed cyclic quadrilateral, an expression that is wrongly attributed to Lhuilier (1782), who proposed the same theory 350 years later.