@inbook{10.2307/j.ctt1r2f46.10,
ISBN = {9780691158204},
URL = {http://www.jstor.org/stable/j.ctt1r2f46.10},
abstract = {An early Hindu work on astronomy, theSurya Siddhanta(ca. 400 A.D.), gives a table of half-chords based on Ptolemy's table (fig. 15). But the first work to refer explicitly to the sine as a function of an angle is theAryabhatiyaof Aryabhata (ca. 510), considered the earliest Hindu treatise on pure mathematics.¹ In this work Aryabhata (also known as Aryabhata the elder; born 475 or 476, died ca. 550)² uses the wordardha-jyafor the half-chord, which he sometimes turns around tojya–ardha(“chord–half”); in due time he shortens it tojyaorjiva.Now begins},
bookauthor = {Eli Maor},
booktitle = {Trigonometric Delights},
pages = {35--40},
publisher = {Princeton University Press},
title = {Six Functions Come of Age},
year = {1998}
}