Surya Siddhanta
त्रिभज्यया भवेच् छङ्कुस् तद्वर्गम् परिशोधयेत् । त्रिज्यावर्गात् पदम् दृग्ज्या छायाकर्णौ तु पूर्ववत्॥
Subtract the square of the Śanku from that of the radius; the square root of the remainder is drịg-jyá or the sine of the zenith distance (at the given time). (From the śanku and the drịg-jyá) find the shadow and its hypothenuse as mentioned before (in Śloka 32). Multiply the radius by the given shadow (of the gnomon) and divide the product by the shadow's hypothenuse.
english translation
tribhajyayA bhavec chaGkus tadvargam parizodhayet । trijyAvargAt padam dRgjyA chAyAkarNau tu pUrvavat॥
hk transliteration by Sanscript