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

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Fig. 54
parallel to the horizon. then Ox = Iṣṭa-S'anku = Oα +
ax = Un-mandala S'anku + Iṣṭa yaṣṭi. ar = yaṣṭi.
In the Southern hemisphere Oα, the Unmandala
S'anku will be below the horizon so that Iṣṭayaṣṭi
decreased by the Unmandala S'anku will be Iṣṭa-S'anku.
Thus we have the method of obtaining the Iṣhta-
S'anku from the Unnata Kāla as detailed above. We shall
see what this process means in modern terms.
Unnatakāla-Charakāla = ⊙P̂A − AP̂E (Fig. 21) =
⊙P̂E where ⊙ is the foot of the declination circle of the
Sun e in any arbitrary position in his diurnal path. But
⊙P̂E = QP̂E − QP̂⊙ = 90−h where h is the hour angle
of the Sun. Thus Sutra = H sin (90−h) = H cos h I