Jyeá¹£á¹Âhadeva () was an astronomer-mathematician of the Kerala school of astronomy and mathematics founded by Madhava of Sangamagrama (). He is best known as the author of the YuktibhÃÂá¹£ÃÂ, a commentary in Malayalam of the treatise Tantrasamgraha by Nilakantha Somayaji. In the YuktibhÃÂá¹£ÃÂ, Jyeá¹£á¹Âhadeva gave complete proofs and rationales for the statements in Tantrasamgraha, which was unusual for traditional Indian mathematicians of the time. The YuktibhÃÂṣàis now believed to contain derivations of Taylor and infinite series expansions for certain trigonometric functions. However, it did not combine several ideas under the unifying concepts of the derivative and the integral, show the connection between the two, or turn calculus into the powerful problem-solving tool we have today. Jyeá¹£á¹Âhadeva also authored Drk-karana, a treatise on astronomical observations.
There are a few references to Jyeá¹£á¹Âhadeva scattered across several old manuscripts. From these manuscripts, one can deduce a few bare facts about the life of Jyeá¹£á¹Âhadeva. He was a Nambudiri belonging to the Parangngottu family (Sanskritised as Parakroda) born about the year 1500 CE. He was a pupil of Damodara and a younger contemporary of Nilakantha Somayaji. Acyuta Piá¹£ÃÂraá¹Âi was a pupil of Jyeá¹£á¹Âhadeva. In the concluding verse of his work Uparagakriyakrama, completed in 1592, Piá¹£ÃÂraá¹Âi referred to Jyeá¹£á¹Âhadeva as his "aged benign teacher". From a few references in Drk-karana, a work believed to be of Jyeá¹£á¹Âhadeva, one may conclude that Jyeá¹£á¹Âhadeva lived up to about 1610 CE. According to K. V. Sarma, the name "Jyeá¹£á¹Âhadeva" is most probably the Sanskritised form of his personal name in the local language Malayalam.
Parangngottu, the family house of Jyeá¹£á¹Âhadeva, still exists in the vicinity of Trikkandiyur and Alathiyur. There are also several legends connected with members of the Parangngottu family.
Little is known about the mathematical traditions in Kerala prior to Madhava of Sangamagrama. Madhava taught Parameshvara Nambudiri, who taught Damodara. Damodara taught Nilakantha Somayaji and Jyeá¹£á¹Âhadeva. Jyeá¹£á¹Âhadeva taught Acyuta Piá¹£ÃÂraá¹Âi, who taught Melpathur Narayana Bhattathiri.
Jyeá¹£á¹Âhadeva is only known to have composed two works, namely the YuktibhÃÂṣàand Drk-karana. The former is commentary on Tantrasamgraha by Nilakantha Somayaji and the latter is a treatise on astronomical computations.
Three factors make the YuktibhÃÂṣàunique in the history of the development of mathematical thinking in the Indian subcontinent: