Person: Kushyar Ibn Labban

Kushyar ibn Labban was a Persian astronomer who wrote an early work on Hindu numerals.

Very little is known of Kushyar ibn Labban's life.
From his works we know that Kushyar was primarily an astronomer who wrote texts on astronomy and geography.
Kushyar's Principles of Hindu reckoning was written about 1000 AD.
It may be the oldest Arabic mathematical text using Hindu numerals, and ibn Labban's concepts reveal considerable originality ...
The first point to note is that Kushyar uses a symbol for zero, but does not use any separating symbol to distinguish the fractional part of a number from the integral part.
Kushyar gives methods to construct exact square roots, as well as approximate methods to calculate the square roots of non-square numbers.
As a check on the accuracy of his results, Kushyar uses the method of "casting out nines" or "checking the nines" which basically checks that the sums are correct modulo 9.

Born 971, Gilan (now in Iran). Died 1029, Baghdad (now in Iraq).

View full biography at MacTutor

Astronomy, Origin Iran

Epochs: 1

Thank you to the contributors under CC BY-SA 4.0!

O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive