Reconstruction of a Greek table of chords / B.L. van der Waerden.
Abstract:
'R.R. Newton has shown that Ptolemy's table of solar declinations ("Almagest" I, 15) was not computed from Ptolemy's own table of chords...Newton explains this by assuming that Ptolemy copied his table...from an earlier source...I shall venture a tentative reconstruction of the method of computation...which was suggested to me by a verse in the Aryabhatiya of Aryabhata.' From the summary
Archive for history of exact sciences Vol. 38 (1988), p. 23-38