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

87 QST at the locality S is a small circle whose circumference is smaller than that of ABC. The problem is now to find the length of this circle QST. Evidently QST / ABC = 2 π r / 2 π R = r / R where r and R are respectively the radii of the two circles. But r / R = Cos ϕ from the triangle OSO', where Ô'₁SO = ŜOA = latitude of the place S. ∴ QST = ABC × Cos ϕ = (ABC × H Cos ϕ) / R I where H Cos ϕ is the Hindu cosine of ϕ known as lambajyā and stands for OS₁ = O'₁S = r. This lambajyā is also called Dyujya if the small circle is the diurnal circle of a Star. The diurnal circle of a Star is called Dyujya-Vritta and its radius is called Dyujyā-Equation I proves the first statement of the Fig. 5 verse. In fig. 5 Gn N is called the fundamental gnomonic triangle where Gn is the vertical gnomon pointing to the Zenith Z of the celestial sphere and is considered to be of 12 units (Angulas as they are called), GN the midday- shadow of the gnomon cast on an equinoctial day when the