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

283 ∴ Kalā = (H cos h × H cos δ) / R II ∴ Iṣṭa-yaṣṭi = [(H cos h × H cos δ) / R] × [(H cos φ) / R] III Now Unmaṇḍala-Śaṅku is derivable from the sixth latitudinal triangle in which Krāntijyā is the Karṇa and Unmaṇḍala-Śaṅku is the Bhuja. Comparing it with the second latitudinal triangle Krāntijyā / R = U. S. / (H sin φ) where U. S. is Unmaṇḍala-Śaṅku. ∴ U. S. = (Krāntijyā × H sin φ) / R = (H sin φ H sin δ) / R IV ∴ Iṣṭa-Śaṅku as per the above formulation is given by Iṣṭa-Śaṅku (I. S.) = (H sin δ H sin δ) / R + (H cos φ H cos δ H cos h) / R² = H cos z V [चित्र: गोलीय त्रिभुज PZS (Spherical triangle PZS) — शीर्ष: Z (zenith), P (celestial pole), S (celestial body / Sun); भुजाएँ: ZP = 90 - φ, ZS = z, PS = 90 - δ; कोण: ∠PZS = 90 - A, ∠ZPS = h, ∠PSZ = η] (Ref. fig. 55) Fig. 55 Formulae for △PZS Z = zenith ; P = celestial pole. S = celestial body, say, the Sun. z = zenith-distance of the celestial body S.