à Ârëdhara or à ÂrëdharÃÂcÃÂrya (8thâÂÂ9th century) was an Indian mathematician, known for two extant treatises about arithmetic and practical mathematics, PÃÂá¹Âëgaá¹Âita and PÃÂá¹Âëgaá¹Âita-sÃÂra, and a now-lost treatise about algebra, Bëjagaá¹Âita.
Very little is known about à Ârëdhara's life beyond mentions of his mathematical work by later mathematicians and the content of his extant treatises, which do not contain biographical details such as his parents, teachers, or birthplace. Various scholars have suggested he came from the Bengal region or from South India. Based on example problems in his works mentioning Shiva, and a dedication in PÃÂá¹Âëgaá¹Âita-sÃÂra, he was probably a Shaivite Hindu.
He was mentioned by BhÃÂskara II (12th century), and made apparent reference to Brahmagupta (7th century). GovindasvÃÂmin (9th century) quoted a passage also found in PÃÂá¹Âëgaá¹Âita-sÃÂra, and overlapping material is found in the work of MahÃÂvëra (9th century), from which historians estimate à Ârëdhara to have lived in the 8th or early 9th century.
He has sometimes been conflated with other medieval Indian scholars also named à Ârëdhara.
à Ârëdhara wrote two extant mathematical treatises. The first, PÃÂá¹Âëgaá¹Âita, also called Bá¹Âhat-PÃÂá¹Âi ("Bigger PÃÂá¹Âi") and Navaà Âatë ("Having 900"), extensively covered the practical mathematics of the time including arithmetic and mensuration (the part of geometry concerned with calculating sizes, lengths, areas, and volumes). It is believed to have originally included 900 stanzas, but only 251 are extant, and many topics mentioned in the table of contents have been lost. The second, PÃÂá¹Âëgaá¹Âita-sÃÂra, also called Trià Âatikà("Having 300") because it was written in three hundred verses, is an abridged summary of PÃÂá¹Âëgaá¹Âita. It discusses counting of numbers, natural number, zero, measures, multiplication, fraction, division, squares, cubes, rule of three, interest-calculation, joint business or partnership, and mensuration.
He also wrote a work on algebra, Bëjagaá¹Âita, which has been lost, but some quotations remain in the works of later mathematicians. Some historians believe that à Ârëdhara may have authored another mathematical treatise called Gaá¹Âita-panÃÂcaviá¹Âà Âë.
His notable works includeâÂÂ