Surya Siddhanta
याम्ययोर् विदिशोः शङ्कुर् एवम् याम्योत्तरे रवौ । परिभ्रमति शङ्कोस् तु शङ्कुर् उत्तरयोस् तु सः॥
If the sun be south of the prime vertical, then the Koṇa-śanku will be south-east or south-west, but if he be north of it, then it will be north-east or north-west. The square-root of the difference between the square of the Koṇa-śanku and that of the radius, is called the Drịgjyá or the sine of the zenith distance.
english translation
yAmyayor vidizoH zaGkur evam yAmyottare ravau । paribhramati zaGkos tu zaGkur uttarayos tu saH॥
hk transliteration by Sanscript