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

192 ∴ (SL cos ω) / (cos δ) = H sin rK. SL = H sin rS ∴ H sin rK = (H sin rS × H cos ω) / (H cos δ) We proved the above in a modern way. The Hindu concept is derived from the similarity of SML and ACM′ where C is the centre of the sphere and M′ is the foot of the perpendicular from A on the plane of the equator ∴ LM / CM′ = SL / CA ∴ LM = (H cos ω × H sin rS) / R Since LM = SN. LM divided by H cos δ and multiplied by R gives H sin rK ∴ H sin rK = [(H cos ω × H sin rS) / R] × [R / (H cos δ)] = = (H cos rS × H cos ω) / (H cos δ) i.e. H sin α = (H sin λ × H cos ω) / (H cos δ) Here H cos ω is called Trigṛha-dyu-maurvī because it is the H cosine of the declination of λ when λ = 90°. Verses 58, 59. The magnitudes of the rising times. Those rising times are 1670, 1793, 1937 ; these in the same and reverse orders diminished or increased by their respective Chara segments which are also in the same and reverse orders give the rising times of the Sāyana Rasis beginning from Meṣa for the locality. The Rasis from Tulā are in a reverse direction i.e. as the Meṣa is proje- cting upwards above the horizon, Tulā will be projecting below the horizon so that, the time taken by Meṣa to rise is exactly the time taken by Tulā to set. Comm. We shall compute the rising times of Sāyana Rasis for Lanka first i.e. for zero latitude using modern methods from the formula tan α = cos ω tan λ