There are a few references to Jyeṣṭhadeva scattered across several old manuscripts.[1] From these manuscripts, one can deduce a few bare facts about the life of Jyeṣṭhadeva. He was aNambudiri belonging to the Parangngottu family (Sanskrtised asParakroda) born about the year 1500 CE. He was a pupil ofDamodara and a younger contemporary ofNilakantha Somayaji.Achyuta Pisharati was a pupil of Jyeṣṭhadeva. In the concluding verse of his work titledUparagakriyakrama, completed in 1592,Achyuta Pisharati has referred to Jyeṣṭhadeva as hisaged benign teacher. From a few references inDrkkarana, a work believed to be of Jyeṣṭhadeva, one may conclude that Jyeṣṭhadeva lived up to about 1610 CE.
Parangngottu, the family house of Jyeṣṭhadeva, still exists in the vicinity ofTrikkandiyur andAlathiyur.[1] There are also severallegends connected with members of Parangngottu family.
Jyeṣṭhadeva is known to have composed only two works, namely,Yuktibhāṣā andDrkkarana. The former is commentary with rationales ofTantrasamgraha ofNilakantha Somayaji and the latter is a treatise on astronomical computations.
Three factors makeYuktibhāṣā unique in the history of the development of mathematical thinking in the Indian subcontinent:
It is composed in the spoken language of the local people, namely, theMalayalam language. This is in contrast to the centuries-old Indian tradition of composing scholarly works in theSanskrit language which was the language of the learned.
The work is in prose, again in contrast to the prevailing style of writing even technical manuals in verse. All the other notable works of theKerala school are in verse.
Most importantly,Yuktibhāṣā was composed intentionally as a manual of proofs. The very purpose of writing the book was to record in full detail the rationales of the various results discovered by mathematicians-astronomers of the Kerala school, especially ofNilakantha Somayaji. This book is proof enough to establish that the concept of proof was not unknown to Indian mathematical traditions.
^(Bressoud 2002, p. 12) Quote: "There is no evidence that the Indian work on series was known beyond India, or even outside Kerala, until the nineteenth century. Gold and Pingree assert that by the time these series were rediscovered in Europe, they had, for all practical purposes, been lost to India. The expansions of the sine, cosine, and arc tangent had been passed down through several generations of disciples, but they remained sterile observations for which no one could find much use."
^J J O'Connor; E F Robertson (November 2000)."Jyesthadeva". School of Mathematics and Statistics University of St Andrews, Scotland. Retrieved28 January 2010.
^K. V. Sarma (1972).A history of the Kerala school of Hindu astronomy (in perspective). Hoshiarpur, Panjab University: Vishveshvaranand Institute of Sanskrit & Indological Studies. p. 59.Bibcode:1972hksh.book.....S.
K. V. Sarma (1972).A history of the Kerala school of Hindu astronomy (in perspective). Vishveshvaranand Indological series. Vol. 55. Vishveshvaranand Institute of Sanskrit & Indological Studies, Hoshiarpur, Panjab University.Bibcode:1972hksh.book.....S.
For a modern explanation of Jyeṣṭhadeva's proof of thepower series expansion of the arctangent function:Victor J. Katz (2009)."12".A history of mathematics: An introduction (3 ed.).Addison Wesley. pp. 450–455.ISBN978-0-321-38700-4.
