Robert of Chester
Encyclopedia
Robert of Chester was an English arabist
Arabist
This is an article about the western scholars known as Arabists, not the political movement Pan-Arabism.An Arabist is someone normally from outside the Arab World who specialises in the study of the Arabic language and Arab culture, and often Arabic literature.-Origins:Arabists began in medieval...

 of the 12th century. He translated several historically important books from Arabic to Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

, by authors such as Abu Musa Jabir Ibn Hayyan and Al-Khwarizmi including:
  • Liber algebrae et almucabola
    The Compendious Book on Calculation by Completion and Balancing
    , also known under a shorter name spelled as Hisab al-jabr w’al-muqabala, Kitab al-Jabr wa-l-Muqabala and other transliterations) is a mathematical book written in Arabic in approximately AD 820 by the Persian (Arabic for "The Compendious Book on Calculation by Completion and Balancing", in...

    Al-Khwārizmī's book about algebra
    Algebra
    Algebra is the branch of mathematics concerning the study of the rules of operations and relations, and the constructions and concepts arising from them, including terms, polynomials, equations and algebraic structures...

     translated in 1145

  • Liber de compositione alchimiae a book about alchemy
    Alchemy
    Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...

     translated in 1144


In the 1140s Robert worked in Spain, where the division of the country between Muslim and Christian rulers resulted in opportunities for interchange between the different cultures. However, by the end of the decade he had returned to England. Some sources identify him with Robert of Ketton
Robert of Ketton
Robert of Ketton was an English medieval theologian, astronomer and Arabist.Ketton, where Robert was either born or perhaps first took holy orders, is a small village in Rutland, a few miles from Stamford.Robert is believed to have been educated at the Cathedral School of Paris...

  who was also active as an Arabic-Latin translator in the 1140s.
However, Ketton
Ketton
Ketton is a village and civil parish in the county of Rutland in the East Midlands of England. It is located about eight miles east of Oakham and three miles west of Stamford in Lincolnshire...

 and Chester
Chester
Chester is a city in Cheshire, England. Lying on the River Dee, close to the border with Wales, it is home to 77,040 inhabitants, and is the largest and most populous settlement of the wider unitary authority area of Cheshire West and Chester, which had a population of 328,100 according to the...

, while both places in England, are a long way apart. Also, when in Spain, Robert of Ketton was based in the Kingdom of Navarre
Kingdom of Navarre
The Kingdom of Navarre , originally the Kingdom of Pamplona, was a European kingdom which occupied lands on either side of the Pyrenees alongside the Atlantic Ocean....

, whereas Robert of Chester is known to have worked in Segovia
Segovia
Segovia is a city in Spain, the capital of Segovia Province in the autonomous community of Castile and León. It is situated north of Madrid, 30 minutes by high speed train. The municipality counts some 55,500 inhabitants.-Etymology:...

.

While translating Al-Khwārizmī's book about algebra
Algebra
Algebra is the branch of mathematics concerning the study of the rules of operations and relations, and the constructions and concepts arising from them, including terms, polynomials, equations and algebraic structures...

, Robert of Chester made an interesting error that lives on today. Arabic script
Arabic alphabet
The Arabic alphabet or Arabic abjad is the Arabic script as it is codified for writing the Arabic language. It is written from right to left, in a cursive style, and includes 28 letters. Because letters usually stand for consonants, it is classified as an abjad.-Consonants:The Arabic alphabet has...

, like Hebrew script, consists of consonants with vowels punctuated underneath and often omitted. The sine
Sine
In mathematics, the sine function is a function of an angle. In a right triangle, sine gives the ratio of the length of the side opposite to an angle to the length of the hypotenuse.Sine is usually listed first amongst the trigonometric functions....

 originated in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, and was adopted by the Arabs who spelled the consonants as "jb". When Robert translated the word, not understanding the Hindu origin, he supplied Arabic vowels yielding the word for bay or inlet. In Latin, a bay or inlet is sinus. And thus, the origin of the trigonometric function named sine
Sine
In mathematics, the sine function is a function of an angle. In a right triangle, sine gives the ratio of the length of the side opposite to an angle to the length of the hypotenuse.Sine is usually listed first amongst the trigonometric functions....

.

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