Surya Siddhanta
क्षेपो भुजस् तयोर् वर्गयुतेर् मूलम् श्रवस् तु तत् । मानयोगार्धतः प्रोज्झ्य ग्रासस् तात्कालिको भवेत्॥
The Moon's latitude is the Bhuja (or base) and the square-root of the sum of the squares of the Koṭi and Bhuja is the hypothenuse (of the triangle as mentioned before in Śloka 18th). Subtract the hypothenuse from half the sum of the diameters (as stated in Śloka 10th); the remainder will be the quantity of the eclipsed part (of the disc) at the time (at which the Koṭi and Bhuja are ascertained).
english translation
kSepo bhujas tayor vargayuter mUlam zravas tu tat । mAnayogArdhataH projjhya grAsas tAtkAliko bhavet॥
hk transliteration by Sanscript