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