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

485 Fig. 113 cular distances between the Udayāstasutras and the East- west line are called Agrās and the perpendiculars from the feet of the S'ankus on the Udayāstasutras are called S'ankutalas which were all defined in the course of the Tripras'nādhyāya. We have from the spherical triangle PZS, sin δ = sin ϕ cos z + cos ϕ sin z sin a so that sin δ / cos ϕ = tan ϕ cos z + sin z sin a which was shown as A=S+B in the Tripras'nādhyāya ie. Agrā = Sankutala + Bhuja. Changing δ into —δ and a into —a we have different formulae, the standard form being A=S+B. We don't propose to change ϕ into —ϕ, because in India this case does not arise. Thus our latitude being north, the S'anku- talas defined above as the distances from the feet of the Sankus from the Udayāstasutras are always deemed as south. It need not be reiterated that the Udayāstasutras