सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

495 Let in fig. 119, ST be the Bhuja, MT the Koti and SM the Karṇa formerly defined. As per verse (5) 6B / K = Valana where B = ST, K = SM, and 6 = MG so that GE = 6B / K = Valana, which is in practice drawn as E'G' from the east point e, in the form of a Hsine. CG goes by the name Valanasūtra. Compute the Śukla in angulas after making the prescribed correction in the longitude of the Moon as stated by Bhāskara and dividing the elon- gation of the Moon, thereafter obtained, by 15. Mark off the Śukla in angulas along the Valanasūtra from G. Suppose GD is the Śukla. Draw the diameter AB perpendicular to the Valanasūtra passing through M. Draw the circle circumscribing D, A, B. Its centre lies evidently on the Valanasūtra, say C. The circle drawn is called Parilekha Vṛtta, its radius CA is called Pari- lekhasūtra and the point C Parilekha Vṛtta Madhya. In the triangle CAM, which is right-angled CA is the Karṇa, AM the Bhuja and MC the Koti. CD is equal to the Karṇa CA so that MD = CD – CM = Karṇa – Koti = K – k (say). We have AM² = CA² – CM² = K² – k² = 36 = B²; Hence K + k = B² / (K – k). Here K – k = MD is known because GD the Śukla is known. So B² / (K – k) = K + k is known. Thus knowing K – k and K + k, by using what is called Saṁkramagaṇita ie. by adding K + k and K – k, we have K and by sub- tracting we have k. Here the Koti CM is called Vibhā and the Karṇa CD the Swabhā. The Parilekhasūtra or the radius of the Parilekha Vṛtta being the Karṇa, the Swabhā is thus the Parilekhasūtra. In the wake of this exposition, the translation of verse (7) runs as follows. "Let the compliment of the elongation (corrected as directed in verse (6)) divided by 15 be the denominator; let the numerator be 36; take the