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

289 Fig. 56 and add Chara to Unnata when δ < 0 and take the H sine of the result. Let us first consider the case when δ > 0. (Refer fig. 56) when the Sun is at ☉, Iṣṭa Śaṅku is H sin ☉L; and Unmandala Śaṅku is H sin BM. When the Sun is at ☉₁, Iṣṭa Śaṅku = H sin ☉₁N. In the first case Iṣṭayaṣṭi = (H sin ☉L — H sin BM) which will be the orthogonal projection of ☉B on the meridian plane. Unmandala Śaṅku and the Iṣṭa Śaṅku in the position ☉₁ are similarly the orthogonal projections of BM and ☉₁N on the same plane. In the position ☉ Iṣṭa Śaṅku = Unmandala Śaṅku + Iṣṭayaṣṭi, whereas in the position ☉₁, Iṣṭa Śaṅku = Unmandala Śaṅku — Iṣṭayaṣṭi which is now downwards. Thus in the place of addition we have subtraction of Iṣṭayaṣṭi. This reversion has arisen out of 37