161 The Sun's drkkṣepajya is the Rsine of the zenith distance of that point of the ecliptic which is at the shortest distance from the zenith.¹ The Moon's drkkṣepajya is the Rsine of the zenith distance of that point of the Moon's orbit which is at the shortest distance from the zenith. THE TEN RSINES A rule for finding the drgjyas (i.e., the Rsines of the zenith distances) of the Sun and the Moon : 20-22. Calculate the Rsine of the Sun's zenith distance (drgjya) from the nadis elapsed (since sunrise in the forenoon) or to elapse (before sunset in the afternoon) in accordance with the method stated before. The method for (finding the Rsine of the zenith distance of) the Moon is now being described. Take the sum or difference of the celestial latitude and declination of the Moon for the time of geocentric conjunction (of the Sun and Moon) according as they are of like or unlike direction. The Rsine of the resulting sum or difference is (the Rsine of) the Moon's (true) declination. From that calculate the day-radius, the earthsine, and the asus of the ascensional difference. With the help of these and the nädis elapsed (since sunrise in the forenoon) or to elapse (before sunset in the afternoon) obtain the Rsine of the zenith distance. (This is the Rsine of the Moon's zenith distance).³ (or Moon's orbit) and C the point of the ecliptic (or Moon's orbit) which is at the shortest distance from Z. Then in the triangle ZCM, Rsin ZM = madhyajya, LZCM 90°, and Rsin MZC = udayajya. Therefore Rsin (arc MC)=(madhyajyā × udayajyā)/R. The final result is obtained by treating the triangle formed of the Rsines of the sides of the triangle ZCM as a plane right-angled triangle (which assumption is however incorrect). The same rule occurs also in SiDV, I, v. 5. ¹.The point of the ecliptic which is at the shortest distance from the zenith is called the nonagesimal or the central ecliptic point. 2 Vide supra, chapter III, stanzas 18-25. This rule for the Rsine of the Moon's zenith distance is evidently approximate,
