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

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[चित्र: Fig. 83 — Equator, Ecliptic, Prime vertical]
Fig. 83
Note 1. Bhāskara says PB' (fig. 82) is Krānti-Sinjanī; so
it is because PB' = PK' sin (90 - λ) = (H sin ω H cos λ) / R
= H sine of the declination of a point whose longitude is
90 + λ = Satribha-grahaja-krānti as is mentioned by
Bhāskara and Sūrya-siddhānta.
Note 2. If M be the centre of the Moon's disc and
ABC its horizon defined above, the arc AB intercepted
between the Ecliptic and the Equator is Āyana Valana, the
arc BC intercepted between the Equator and the prime-
vertical is Ākṣa Valana and the arc AC intercepted
between the Ecliptic and the prime-vertical is Sphuta-
Valana.
Note 3. The analysis of Ākṣa Valana proceeds on
similar lines, only we have P and N in the place of K
and P.
Note 4. The mistake of Lallāchārya alluded to by
Bhāskara is as follows. The Āyana Valana, we have seen
is zero at the Ayanas ie. the solstices and maximum at
♈ and ♎ ie. the equincotial points removed by 90° from
the Ayanas. Now Hversine = R — H cosine so that when
90 — λ = 0 ie. λ = 90°, Hversine (90 — λ) = R — H cos (90 — λ)
= R — H sin 90° = R — R = 0 and when 90 — λ = 90° ie.
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