Jyesthadeva (* 1500 in Kerala, † 1575 in Kerala ) was an Indian mathematician and astronomer.

Jyesthadeva belonged to the Kerala school of mathematicians and astronomers, who also Madhava (1350-1425), Parameshvara (around 1370-1460 ) and Nilakantha Somayaji ( 1444-1544 ) belonged on which he established. He was like Nilakantha a student of Damodara, son of Parameswara. He was among the Nambudiri Brahmins.

He is responsible for the astronomical treatise Yutikbhasa (also known Gaṇitanyāyasaṅgraha called ), in particular on the Tantrasamgraha of Nilakantha (it was completed in 1501 ) builds. It deals with mathematical astronomy ( such as movement of the planets, sun and moon, eclipses, rising and setting transition times of the heavenly bodies ), somewhat in the manner of Tycho Brahe in Europe, and is written in Malayalam, a local language in Kerala. It is dated around 1550.

Of particular importance is the unusual Indian texts for presentation of evidence of mathematical theorems. Probably it was written with the intention to record the evidence of the text of Nilakantha and showing that the evidence concept in Indian mathematics was well known.

Of particular interest are series expansions for arc tangent, sine and cosine ( according to the Maclaurin series ) that were known Madhava, however, were discovered in Europe by James Gregory and Isaac Newton until about 250 years after Madhava. Madhava get so among other things, accurate values ​​for Pi and values ​​for sines. Because of this infinite series ( the first such in addition to the geometric series ) mathematicians of this school have been filed also among the founders of analysis and it has been speculated about a possible spread of the results to the West via merchants or Jesuit missionaries. There are, however, no evidence. Even within India, the Kerala school was isolated, partly because of the language differences. In other Indian mathematical texts outside the Kerala school Sanskrit has traditionally been used. The Yutikbhasa used contrary to the tradition ( in Kerala ) no verse of the text.

There are also other mathematical advances in Yutikbhasa as first convergence tests. (In Augustin- Louis Cauchy )

The first indications of the Yutikbhasa and their significance derived from the English administrative staff and Malayalam specialists Charles Matthew Whish (1794-1833), who also published in 1834 in the Transactions of the Royal Asiatic Society.

One of the students of Jyesthadeva was Achyuta Pisharati (around 1550-1621 ).