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

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PZ = colatitude ; PS = north-polar-distance or co-decli-
nation.
η is called the parallactic angle ; h = hour-angle of S.
(90 — a) = The complement of the Hindu
azimuth a being measured from the East point.
cos (90 — δ) = cos (90 — φ) cos z + sin (90 — φ) sin z cos (90 — a)
sin δ = sin φ + cos z + cos φ sin z sin a (1)
cos z = cos (90 — φ) cos (90 — δ) + sin (90 — φ) ×
sin (90 — δ) cos h
= sin φ sin δ + cos φ cos δ cos h (2)
cos (90 — φ) cos (90 — a) = sin (90 — φ) cot z — sin (90 — a) cot h
ie. sin φ sin a = cos φ cot z — cos a cot h (3)
cos (90 — φ) cos h = sin (90 — φ) cot (90 — δ) — sin h ×
cot (90 — a)
ie. sin φ cos h = cos φ tan δ — sin h tan a (4)
sin z sin (90 — δ)
─────── = ───────────── ie. sin z cos a = sin h cos δ (5)
sin h sin (90 — a)
This means in modern terms
cos z = sin φ sin δ + cos φ cos δ cos h V which we
derive from the triangle PZS.
Verse 58. To get H cos z from h the hour-angle or
nata Kāla.
The H. vers (Nata) is called Sara (CQ of fig. 52) (29)
Antyā — Śara = Iṣṭāntyā ie. FQ — CQ = FC = AN
(fig. 51)
H cos δ Śara × Kujyā
Śara × ───────── = ───────────── = phala (CQ) (fig. 53)
R Charajyā
(30)