A History of Sanskrit Literature c35.s2.4

c35.s2.4

The evidences of Greek derivation in the Siddhāntas, and still more plainly in later works, may be summed up as follows.² The division of the ecliptic into the Nakṣatras yields to that into the signs of the zodiac, with names borrowed from the Greek; the motions of the planets, hitherto neglected, come to be explained by the doctrine of epicycles; the notion of parallax and methods of calculating it were introduced; new methods of calculating eclipses appear; the heliacal rising and setting of heavenly bodies was studied, especially with astrological reference; correct measurements of day and night were achieved; the length of the year was revised; and the names of the planetary week-days were introduced. We find already in the *Pauliça*—perhaps also in the other Siddhāntas—an important contribution to Indian trigonometry, in the shape of a table of sines, which seems clearly to have been borrowed from Ptolemy's table of chords, the device being adopted of dividing the radius not into sixty parts with Ptolemy but into 120 parts, thus enabling the value given for the chords to be taken over bodily for the sines of half the angles. It is only in Āryabhaṭa that we find the radius as 3438' with the necessary change of sine values.