Abu'l-Hasan ibn Ali al-Qalasadi

Abū'l-Ḥasan ʿAlī ibn Muḥammad ibn ʿAlī al-Qurashī al-Qalaṣādī (

Al-Qalaṣādī was born in Baza, an outpost of the Emirate of Granada. He received education in Granada, but continued to support his family in Baza. He published many works and eventually retired to his native Baza.

His works dealt with Algebra and contained the precise mathematical answers to problems in everyday life, such as the composition of medicaments, the calculation of the drop of irrigation canals and the explanation of frauds linked to instruments of measurement. The second part belongs to the already ancient tradition of judicial and cultural mathematics and joins a collection of arithmetical problems presented in the form of poetical riddles.

In 1480 the Christian forces of Ferdinand and Isabella, "The Catholic Monarchs", raided and often pillaged the city. Al-Qalasādī served in the mountain citadels which were erected in the vicinity of Baza. Al-Qalasādī eventually left his homeland and took refuge with his family in Béja, Tunisia, where he died in 1486. Baza was eventually besieged by the forces of Ferdinand and Isabella and then sacked.

Symbolic algebra

Like his predecessors, al-Qalaṣādī used an

• ﻭ (wa) means "and" for addition (+)
• إلا (illa) literally, "except"; means "less" for subtraction (-)
• في (fi) literally, "in"; means "times" for multiplication (*)
• على (ala) means "over" for division (/)
• ﺝ (
  root
  "
• ﺵ (sh) represents shay' meaning "thing" for a variable (x)
• ﻡ (
  m) represents morabba'a for a square
  (x²)
• ﻙ (
  k) represents moka'aab for a cube
  (x³)
• ﻝ (
  l) represents ya'adilu for equality
  (=)