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

342 the necessity for knowing the value of CN at any subse- quent moment arises. β, of course, could be computed, knowing the hourly variation of β, which in its turn could be known, by a knowledge of the hourly variation in λ, the longitude of the Sapātachandra. The magnitude of CN is calculated by the rule of three "If by the Sparsa-Sthiti-Khanda we have initially the initial value of CN, what shall we have for (T –t) ?" The result is [(T–t) × CN] / T where CN is the initial value of CN and T the Sparsa-Sthiti-Khanda. Substituting the values of CN and T from verse 12, where CN = √((R+r)²–β²) and T = [√((R+r)²–β²) × 60] / (m₁–s₁) we have the required Bhuja as [(T–t) (√(R+r)²–β²)] / [60 (√(R+r)²–β²)] × (m₁–s₁) = [(T–t) {m₁–s₁}] / 60 minutes = (T–t) (m₁–s₁) degrees as given. Similarly we could find the Bhuja with respect to 'totality' ie. the 'Marda-Bhuja' as it is called. Note. One might mistake M₁ M₂ of fig. 74 (M₁ per- taining to a subsequent moment) to be the Bhuja defined above, which is the join of the centre of the eclipsing body and the foot of the latitude at the middle of the eclipse. That is why Bhāskara uses the word 'Madhya-Sarāgra- Chihna' in the commentary, meaning thereby not the foot of the actual latitude at the middle of the eclipse but only the point N of fig. 77 which 'signifies' it. Second half of verse 16 and first half of verse 17. Taking the latitude of the Moon at a given time as Koti, and Bhuja as the Bhuja of the moment defined above, we have the Karṇa of the moment as √(Bhuja² + β²); R+r–Karṇa gives the Grāsa at the moment.