Equals sign
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The equal sign, equals sign, or "=" is a mathematical symbol used to indicate equality. It was invented in 1557 by Welshman Robert Recorde. The equals sign is placed between the things stated to be equal.
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[edit] History
The "=" symbol that is now universally accepted in mathematics for equality was first used by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557). The original form of the symbol was much wider (longer) than the present form. In his book[1], Recorde explains his design: to auoide the tediouse repetition of these woordes: is equalle to : I will sette as I doe often in woorke use, a paire of paralleles, or Gemowe [i.e. "twin"] lines of one lengthe, thus: =, bicause noe .2. thynges, can be moare equalle. However, a manuscript from the University of Bologna, dated from 1550–1568, features the same equality symbol, possibly earlier than Recorde's use.[citation needed] According to Scotland's St Andrews University Maths History website[2], "The symbol '=' was not immediately popular. The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, was widely used into the 1700s."
[edit] Related symbols
A symbol used to denote items that are approximately equal is "≈" (wave lines), and the symbol used to denote when items are not equal is "≠" (slashed equal sign). Most programming languages, which are limited to the ASCII character set, use "~=", "!=", "=/=" or "<>" to represent "not equal to"; "!=" has carried over into newsgroups and Internet forums. The symbol "≡" is often used to indicate an identity, or a congruence relation in modular arithmetic.
In programming languages, the equals sign may either denote a boolean operator to test equality of values (sometimes a double equal sign "=="), or it may denote an assignment (sometimes denoted with a colon-equals ":="). In some programming languages such as PHP a triple equal sign ("===") denotes equivalence[3], meaning that not only do the two values parse to be the same, they are of the same data type. (For instance, in many scripting languages ("0 == false") is true, but ("0 === false") is not.)
Equality of truth values, i.e. bi-implication or logical equivalence, may be denoted by various symbols including =, ~, and <=>.
[edit] Japanese use
In Japanese, the use of an ＝ in between a person's given name and surname denotes that it is in the Western order. Normally, Japanese names are given as surname first. An example of this in practice would be for the video game character Sol Badguy, which is written as ソル＝バッドガイ in Japanese. Without the ＝, a Japanese reader could mistakenly assume that his surname was "Sol".
[edit] See also
[edit] References
- Cajori, Florian (1993). A History of Mathematical Notations. New York: Dover (reprint). ISBN 0-486-67766-4.
- Boyer, C. B.: A History of Mathematics, 2nd ed. rev. by Uta C. Merzbach. New York: Wiley, 1989 ISBN 0-471-09763-2 (1991 pbk ed. ISBN 0-471-54397-7)
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