# Signal Source

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## Addition (+) and Subtraction (-)

The regular use of the + sign (plus) appears in John Widman d'Eger's Commercial Arithmetic published in Leipzig in 1489.

However, they represented not to the addition or subtraction or positive or negative numbers, but to excesses and deficits in business problems. The positive and negative symbols came into general use only in England after they were used by Robert Record in 1557..The positive and negative symbols were used before they appeared in writing. For example, they were painted on drums to indicate whether the drums were full or not.

The ancient Greek mathematicians, as noted in Diophantus's work, merely indicated the addition together by the plots - a system that we still adopt today when we want to indicate the sum of an integer with a fraction. As a sign of operation more the Italian algebraists used the letter Pinitial Latin word plus.

## Multiplication (.) And division (:)

The sign of X, as we indicate multiplication, is relatively modern. English mathematician Guilherme Oughtred first employed him in the book Clavis Matematicae published in 1631. That same year, Harriot, to also indicate the product to be made, placed a point between the factors. By 1637 Descartes was already limited to writing the juxtaposed factors, thus abbreviating any product. In Leibniz's work is the sign to indicate multiplication: this same inverse symbol indicated division.
The point was introduced as a symbol for multiplication by G. W. Leibniz. On July 29, 1698, he wrote in a letter to John Bernoulli: "I do not like X as a symbol for multiplication because it is easily mistaken for x; I often relate the product between two quantities by a dot. Hence, in designating the relationship I use not one point but two points, which I also use for division. "
The a / b and , indicating the division of a by b, are attributed to the Arabs: Oughtred, and, 1631, placed a point between the dividend and the divisor. The ratio between two quantities is indicated by the sign :, which appeared in 1657 in a work by Oughtred. The sign ÷, according to Rouse Ball, resulted from a combination of two existing signals - and:

## Relation Signs (=,)

Robert Recorde, an English mathematician, will always have his name pointed to in the history of mathematics because he was the first to use the = sign to indicate equality. In his first book, published in 1540, Record placed the symbol between two equal expressions; the sign =; consisting of two small parallel strokes, appeared only in 1557. Some authors comment that in the manuscripts of the Middle Ages the sign = appears as an abbreviation of the word est.
Guilherme Xulander, a German mathematician, pointed to equality at the end of the sixteenth century by two small vertical parallel features; until then the word aequalis appeared at length, linking the two members of equality.

The> (greater than) and <(less than) signs are due to Thomaz Harriot, who greatly contributed his work to the development of algebraic analysis.

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