Abu Mahmud Khujandi
Khujand's position on the Silk Road made it not only a centre for trade but also a melting pot for new ideas. Indeed, one of the finest scientific minds of the 10th century was born in the city and is colloquially known asal-Khujandi ('the one from Khujand').
Abu Mahmud Hamid ibn Khidr Khujandi was born in Khujand in the mid-9005. He worked in the fields of astronomy and mathematics, and made notable discoveries in both.
In Iran he constructed a giant mural sextant to determine the tilt of the earth (which he decided to be 23°32'19"for the year 994) and concluded that the axial tilt is in fact decreasing. The slight inaccuracy in his calculations is likely due to the weight of his instruments.
In mathematics Khujandi stated a special case of Fermat's last theorem, for n=3, and he may also have discovered the spherical law of sines, though surviving texts on this point are inconclusive.