The few facts about Khujandi's life that are known come from both his surviving writings and comments made by Nassereddin Tusi. From Tusi's comments it is fairly certain that Khujandi was one of the rulers of the Mongol tribe in the Khudzhand region, and thus must have come from the nobility.
Al-Khujandi accurately computed the axial tilt to be 23°32'19" (23.53°),[2] which was a significant improvement over the Greek estimate of 23°51'20" (23.86°)[3] and still very close to the modern measurement of 23°26' (23.44°).
Mathematics
In Islamic mathematics, he stated a special case of Fermat's last theorem for n = 3, but his attempted proof of the theorem was incorrect. The law of sines may have also been discovered by Khujandi, but it is uncertain whether he discovered it first, or whether Abu Nasr Mansur or Abul Wafa discovered it first.
^ Richard P. Aulie (1994), "Al-Ghazali Contra Aristotle: An Unforeseen Overture to Science In Eleventh-Century Baghdad", PSCF45: 26-46 (cf.References, 1001 Inventions)