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

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Bhāskara's proof proceeds in two stages from first
principles. In the first place when V coincides with z,
Lambana is seen to be equal to 4 nādis on the horizon and
zero at Z ie. it is zero when H sin Z☉ = 0 and 4 nādis,
a maximum when H sin Z☉ = R. So, it is meet that
Lambana should be taken to be proportional to H sin Z☉
ie. proportional to natajyā. In this context the lambana
termed as Madhyamalambana is entirely along the ecliptic.
It is taken to be in the form of Karṇa, because in the
position of ☉C also it is in the form of a Karṇa.
Then let the Ecliptic be deflected from the zenith
(deflected = क्षिप्त). Vitribhalagna then being deflected
from the position of Z, occupies the position of V (fig. 92).
So ZV is called Dṛk-kshepa since the Ecliptic which was
in the form of a Dṛk-mandala is deflected from that posi-
tion. Also the circle ZV is called Dṛk-kshepa-mandala
because V is deflected along that circle. Now consider
the △ whose sides are H sin ZV, H cos ZV and R.
H cos ZV equal to R and as such in the form of a Karṇa
corresponds to the Madhyamalambana which is also in the
form of a Karṇa ; when this Vitribha-Sanku assumed the
form H cos ZV, ie. rendered a Kōti from its form of a
Karṇa, R, the Sphutalambana is also rendered a Kōti in
the form of ☉ D so that
Madhyamalambana / R = Sphutalambana / H cos ZV
∴ Sphutalambana = (H cos ZV / R) Madhyamalambana
= (H cos ZV / R) × (4 H sin Z☉ / R) .
Then Bhāskara says that we could look at this, from
another angle in the words “यदेव स्फुटलम्बनस्य कोटिरूपत्व-
मुपपन्नम् etc. ”.