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{{T|inglese|biografie|giugno 2019}}
'''Abū l-Ḥasan ibn ʿAlī ibn Muḥammad ibn ʿAlī al-Qalaṣādī''' ({{lang-ar|أبو الحسن علي بن محمد بن علي القرشي البسطي}}; 1412–1486) fu un [[musulmano]] [[arabo]]<ref>{{cite book|last1=Karpinski|first1=Louis Charles|title=The history of arithmetic|date=1965|publisher=Russell & Russell|url=https://books.google.com/?id=7l4LAQAAIAAJ&q=al-kalasadi+%22spanish+arab%22&dq=al-kalasadi+%22spanish+arab%22|language=en}}</ref> [[Matematica islamica|matematico]] di [[al-Andalus]], ''[[faqih]]'' specializzato nel diritto ereditario.
Al-Qalaṣādī è noto per essere stata una delle voci più influenti nella [[Notazioni matematiche|notazione algebrica]] e per aver intrapreso i primi passi verso l'introduzione del simbolismo [[algebra|algebrico]]. Scrisse numerosi libri di [[aritmetica]] e di algebra, tra cui una ''al-Tabṣīra fī ʿilm al-ḥisāb'' ({{lang-ar|التبصير في علم الحساب}} "''Chiarimento sulla scienza del calcolo (i.e. sull'aritmetica)''").
==Gioventù==
Al-Qalaṣādī nacque a [[Baza]], nel [[Sultano|Sultanato]] di [[Granada]]. Ricevette la sua istruzione a[[Granada]], pur seguitando a vivere con la sua famiglia a Baza. Pubblicò vari lavori e infine si ritirò nella sua natia Baza. Trascorse sette anni a [[Tlemcen]] (attuale [[Algeria]]), dove studiò sotto la guida di studiosi [[berberi]] locali, il più importante dei quali si chiamava Ibn Zaghu.
[[File:Granada by Piri Reis.jpg|350px|thumb|right|Mappa del ''Kitāb Baḥriyye'' di [[Piri Reis]] della costa del Sultanato di Granada ([[XVI secolo]]).]]
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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 little arithmetical problems presented in the form of poetical riddles
In 1480 the [[Christians|Christian]] forces of [[Ferdinand II of Aragon|Ferdinand]] and [[Isabella I of Castile|Isabella]], "The Catholic Monarchs", raided and often pillaged the city, al-Qalasādī himself 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 its inhabitants sacked.
==Symbolic algebra==
Like his predecessors al-Qalaṣādī made attempts at creating an [[Mathematical notation|algebraic notation]]. However, these symbols were not the invention of al-Qalaṣādī. The same ones had been used by other mathematicians in North Africa 100 years earlier.<ref name=MacTutor/> Al-Qalaṣādī represented [[Table of mathematical symbols|mathematical symbols]] using characters from the [[Arabic alphabet]], where:<ref name=MacTutor/>
*ﻭ (''[[Waw (letter)|wa]]'') means "and" for [[addition]] (+)
*ﻻ (''[[Illa (Arabic)|illa]]'') means "less" for [[subtraction]] (-)
*ف (''[[Fāʾ|fi]]'') means "times" for [[multiplication]] (*)
*ع (''ala'') means "over" for [[Division (mathematics)|division]] (/)
*ﺝ (''[[Ǧīm|j]]'') represents ''jadah'' meaning "[[Root of a function|root]]"
*ﺵ (''[[Shin (letter)|sh]]'') represents ''shay'' meaning "thing" for a [[Variable (mathematics)|variable]] (x)
*ﻡ (''[[Mīm|m]]'') represents ''moraba'a'' for a [[Square (algebra)|square]] (x<sup>2</sup>)
*ﻙ (''[[Kāf|k]]'') represents ''moka'ab'' for a [[Cube (algebra)|cube]] (x<sup>3</sup>)
*ﻝ (''[[Lām|l]]'') represents ''ya'adilu'' for [[Equality (mathematics)|equality]] (=)
As an example, the equation <math>2x^3 + 3x^2 - 4x + 5 = 0</math> would have been written using his notation as:
<span style="font-size:125%;"> 2<SPAN dir="ltr">ﻙ</SPAN> <SPAN dir="ltr">ﻭ </SPAN> 3<SPAN dir="ltr">ﻡ</SPAN> <SPAN dir="ltr">ﻻ</SPAN> 4<SPAN dir="ltr">ﺵ</SPAN> <SPAN dir="ltr">ﻭ</SPAN> 5 <SPAN dir="ltr">ﻝ</SPAN> 0 </span>
<-->
==Voci correlate==
*[[Matematica]]
*[[Scienziati e studiosi del mondo arabo-islamico]]
==Note==
<references/>
==Bibliografia==
* {{cite journal|first=Ulrich|last=Rebstock|title=Arabic Mathematical Manuscripts in Mauretania|journal=Bulletin of the School of Oriental and African Studies|volume=52|issue=3|year=1990|pages=429–441|jstor=618117|doi=10.1017/s0041977x0015133x}}
* {{Cite book
| first=Carl B.
| last=Boyer
| authorlink=Carl Benjamin Boyer
| title=A History of Mathematics
| edition=Second
| publisher=John Wiley & Sons, Inc.
| year=1991
| isbn=978-0-471-54397-8
| ref = harv
}}
==Collegamenti esterni==
* {{cite encyclopedia | last = Saidan | first = A. S. | title=Al-Qalaṣādī (or Al-Qalaṣādī), Abu 'L-Ḥasan 'Alī Ibn Muḥammad Ibn 'Alī | url=http://www.encyclopedia.com/doc/1G2-2830903548.html | encyclopedia = [[Dictionary of Scientific Biography|Complete Dictionary of Scientific Biography]] | publisher = Encyclopedia.com | origyear=1970-80 | year = 2008 }}
{{Portale|Matematica}}
{{DEFAULTSORT:Qalasadi, Abu Hasan Ali}}
[[Categoria:Matematici|arabi]]
[[Categoria:Giuristi|arabi]]
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