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

302 Comm. Ref. fig. 52. I.A. = AN. I.A. - Carajyā = B.N. Hvers⁻¹ (BN) = arc EN. Arc EN + Caracāpa = EN + EM = MN. This converted into time is evidently the Unnatakāla because the arc MN of the equator is the arc intercepted between the feet of the declination circles at rising and at the time concerned M being the foot of the rising declination circle and N the foot of that at the time in question. The convention of signs is clear. Verse 70 and first half of 71. To obtain the Sun's longitude from the shadow S. The gnomonic shadow at noon, being multiplied by R and divided by K, the inverse H sine of the result gives the meridian zenith-distance. This being decreased or increased by the latitude gives the Sun's declination according as the extremity of the shadow is north or south. From the declination, we have the Sun's longitude by the formula H sin δ = (H sin λ H sin ω) / R . Comm. We have from the triangle formed by the gnomon and the shadow S, S / K = sin z or SR / K = H sin z ∴ H sin⁻¹ (SR / K) = z. Since we are directed to take the mid-day shadow, we have the meridian zenith-distance and from the formula z + δ = φ we have δ. If the extremity of the shadow be north, the Sun is south of the zenith, and then φ ~ z = δ. The word वियुक्ताः is used to signify difference which is positive. If z > φ then the declination is south and vice-versa. If the extremity of the shadow is on the south, the Sun is on the north of the zenith. in which case φ + z = δ. Second half of verse 71. To obtain φ from δ.