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

236 calculating the bhuja ω'M and Koti CM; Bhuja and Koti being known, and the shadow Cω' being drawn, holding two rods whose lengths are equal to the bhuja and Koti perpendi- cular to each other, one extremity of the bhuja-rod being held at ω' and one extremity of the Koti-rod being held at C, and the rods making a right angle at M, then the bhuja-rod determines the north-south direction and the Koti-rod the East-West dire- ction. Fig. 36 Verse 10. The Bhuja is defined as the distance of the extremity of the shadow from the east-west line where the S'anku or gnomon is placed at the intersection of Eω and NS. Koti = √(S² − b²) ∴ Koti will be in the East-West direction. So Chayā-koti = K sin z cos a (7). Comm. Easy. Verse 11. The Chayākarṇa, K is equal to √(S² + 12²), so that √(K² − 12²) = S or √[(K + 12) (K − 12)] = S. Comm. Easy. Verse 12. The S'anku is also called Nara or Nā. The zenith-distance of the Sun at Noon when the Sun is in ♈ is the latitude of the place, called pala or Aksha; the altitude then is called lamba or colatitude. Comm. The word S'anku we have previously used for the gnomon. It is also used for the H cosine of the zenith-distance and to differentiate it from the previous S'anku called Dwādasāṅgul'a-S'anku or twelve-unit-length S'anku, it is termed Mahā S'anku and occasionally Iṣṭa-S'anku. Mahā S'anku or Iṣṭa S'anku = H cos z (8). Thus in figure (37) ☉M = H cos z. In the fig. where gn = gnomon, go = S