Thanks to mathematics, the symbol "X" is strongly associated with many people with something mysterious and mysterious. Today there is no single answer about the nature of the origin of this mathematical symbol, however there are several hypotheses whose authors are trying to explain this riddle.

History of the appearance of the letter X in mathematics

For the first time, the famous mathematician from Alexandria, Diophantus, decided to designate an unknown number with an alphabetic symbol in the 3rd century. In his system, alpha with a dash meant one, beta two, and so on. With (iota), he began to count tens, and with P (ro) hundreds. The number 27 was completed by the 27th letter T (sampi), which meant 900. In this case, the next letter sigma did not get its end number, therefore Diophantus considered it logical to use it as a symbol of an unknown number.

Version number 1 "Arab"

The Arab group of peoples has become famous for many scientific discoveries, among which achievements in the field of mathematics stand apart. It is believed that it was in the countries of the Middle East that equations and decimal fractions were created, local scientists learned to derive roots and coined the term "algebra", which literally translates as "the doctrine of relations, permutations, and solutions."

Interesting fact: the oldest of the existing universities -University of Carwain, founded in 859 in the city of Fes (Morocco).

The emergence of algebra is associated with the activities of a talented native of Khorezm Al-Khorezmi, who studied methods of solving mathematical equations. In his writings, the researcher described the train of thought in words, without using digital or alphabetic characters to indicate formulas. If unknown quantities were encountered, he wrote them down as “necks”, which in Arabic means some thing. This word in the local language corresponded X sign. After the Arabs conquered the Iberian Peninsula, the process of cultural integration with the local population begins. Among the many books, the Spaniards translated the works of Al-Khwarizmi. In the European version, the unknown was written as xei. For greater convenience, writing formulas reduced the designation to one first letter and it turned out "X".

Version number 2 "European"

Continued the work of the Alexandrian scientist Diophantus, the Frenchman François Viet (1540-1603), who became the founder of symbolic algebra. He introduced the scientific circulation of alphabetic characters for writing quantities. A series of vowels (a, I, o, u, e) for the known, and consonants for the unknown (c, b, d, f).

The notation we are used to today - the letters of the beginning of the Latin alphabet as known quantities (a, b, c, d) and the last letters as unknowns (x, y, z) was first used in the 17th century by the famous French thinker Rene Descartes (1596-1660), which stood at the origins of analytic geometry.

In his work "Geometry", which was published in 1637 and is the only one devoted exclusively to mathematics, the author mentions the symbol "X" borrowed from the Spaniards.In French, it was pronounced "ks" and was called "X". Since the unknown value in the majority of mathematical expressions is the same, most often they used “X”, which allowed this symbol to bypass the popularity of others.

Scientists from different countries and eras have worked directly or indirectly on the symbol of the unknown. Diophantus and Viet proposed the principle of alphabetic designation of numbers. The Arab mathematician Al-Khwarizmi came to the same thought, and after the translation of his books by the Spaniards in the 11th century, the Europeans received the designation “X”. In the XVII century, R. Descartes introduced it into a wide scientific circulation.