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

240
Fig. 39
or in modern terms sin δ = sin ϕ cos z + cos ϕ sin z sin a
as derived from the triangle PZS. Formula I is with
respect to the Mahā Śaṅku ⊙ L of fig. 40; if it be reduced
to the Śaṅku of the gnomon the Śaṅku-bhuja ⊙ N becomes
the Chāyābhuja pr which will be equal to
(H sin z H sin a / R) × (K / R) = K sin z sin a whereas,
Agrā becomes (R H sin δ / H cos ϕ) × (K / R) = (K sin δ / cos ϕ) which is called
Karṇāgrā and Śaṅku-tala becomes
(H cos z tan ϕ × K / R) = K cos z tan ϕ = 12 tan ϕ = s,
which is a constant quantity. It will be noted that
Karṇāgrā differs from point to point since K differs from
time to time during a day. In fact Karṇāgrā is the
perpendicular dropped from the extremity of the shadow