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

422
In fig. 92, H sin Z☉ is in the form of a Karṇa;
H sin ZV is in the form of the corresponding Bhuja. This
triangle formed by these two as sides may be taken to be
similar to the triangle ☉DC, both being called parallax
Δs. This plane triangle ☉DC is like the plane triangle
which has for its sides H sin λ, H sin δ, where λ and δ
are the longitude and declination of a point of the Ecliptic.
In the Triprasnādhikara, we had occasion to deal
with this triangle and there we had R
√(H sin² λ - H sin² δ)
--------------------- H sin α where α is the right ascen-
H cos δ
√(H sin² Z☉ - H sin² ZV)
sion of the point. Similarly R ------------------------
H cos ZV
= H sin V☉. In other words Dṛk-nati is H sin V☉
projected into a circle of radius H cos ZV from a circle
of radius R. We have the proportion
∴ C☉ CD D☉
-------- = ------------- = -------------------------
H sin Z☉ ☉ sin ZV √(H sin² Z☉ - H sin² ZV)
D☉ = Sphutalambana
= -------------------------
√(H sin² Z☉ - H sin² ZV)
The quantity under the radical in the denominator
is called Dṛk-nati for the following reasons.
When V coincides with Z, V ☉ is the Dṛk-mandala-
nata, so that when V is deflected also, we continue
to view the Dṛk-nati placed along V☉. Since Madhyama-
lambana ☉C is in the form of a Karṇa in the Δ ☉DC,
we perceive it to be in the form of a Karṇa even when
V coincides with Z. This Madhyamalambana being equal
to Sphutalambana when V coincides with Z, Sphuta-
lambana is also in the form of a Karṇa then. Now in the
position ☉DC, Sphutalambana has assumed the position
of a Kōti ie. the Sphutalambana which, in the form of a
Karṇa, being placed along Dṛk-mandala natāmsa, is now