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

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(3) Why H cos δ is called Dyujyā in formula II
is clear from fig. 20 wherein p is the celestial pole, (C) is the
Fig. 20
celestial Equator and (C) is the diurnal circle of a celestial
body say the ☉ ie. the Sun. Let ☉N be the perpendicular
dropped from ☉ on the plane of the Equator so that
☉N = H sin ☉A = H sin δ CN = H cos δ = C☉ =
radius of the diurnal circle called Dyujyā (Dyu = day)
द्युवृत्तत्रिज्या = द्युज्या (Madhyamapadalōpi Samāsa) formulae
IV, V and VI will be dealt with in the next chapter
Triprasnādhyāya more elaborately but one has to under-
stand what Charajyā is to follow the subsequent verses of
this chapter so that we shall give its location and defini-
tion in the light of fig. 21. Let fig. 21 represent the
celestial sphere in which SEN = Horizon, Z = Zenith,
N = Nadir Ez = prime vertical EQR = celestial equator.