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

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formula cos ω = sin (90-δ) cos v or in the Hindu form
H cos v = (R H cos ω) / (H cos δ) . In this case β' = (β H cos ω) / (H cos δ) .
Or again noting that M K̂ P = 90-λ where λ is the
longitude of R, we could use 'Inner side Inner angle
formula' with respect to the triangle KMP, which gives
0 = sin 90 cot δ - sin (90 -λ) cot v or cot v = cot ω / cos λ
or tan v = cos λ tan ω. But this formula implies the
tangent functions which were not used by the Hindu
astronomers.
Similarly using the elements 90-λ, 90°, v, and 90-δ
of the same triangle KMP, another formula could be got
for v. Or again noting that K P̂ M = 90+α, we could yet
get more formulae where α is the Right ascention of M.
Note (4) Thus far we have used modern formulae.
Let us now see as to how Bhāskara derives his formula.
He takes the triangle MKP' (fig. 107) wherein MK = 90°,
KP' = v and P̂' = 90. From fig. 108, the Hsine of MK is
Fig. 108
KO equal to R where 'O' is the centre of the sphere and
the Hsine of KP is KN so that it is the Āyanavalanajyā,
Hence