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

290
the fact that in the position ☉, Sūtra is the H sine of
(KA — KE) whereas in the position ☉₁ Sūtra is the H sine
of EC ie. H sine of (KE — KC) ie. in the former position
Sūtra = H sine (Unnata-Chara) and in the lattter Sūtra =
H sin (Chara-Unnata). Thus a reversion in subtraction
here, effects a reversion of addition of the Iṣṭayaṣṭi.
Similar is the case in the other cases cited by Bhāskara.
Analytically this happens so because cos h, when h > 90,
becomes negative and adding cos h tantamounts to
subtracting sin θ where h = 90 + θ.
Verse 64. Another point to be observed.
Hvers (90 + θ) = R — H cos 90 + θ̅ = R + H sin θ.
The Unmandala Sanku is not observable when δ is
south in as much as it is below the horizon ; none the less
it may be computed for the purposes of effecting proportion.
Fig. 57
Hvers (CG) = Hvers (CÔG) = GH
Hvers (EG) = Hvers (EÔG) = Hvers (90 + θ)
= R + OH' = R + EL = R + H sin ☉
as defined by Bhāskara,