Equal sign
=



Mathematical signs  
arithmetic  
Plus sign  + 
Minus sign   , ./. 
Mark  ⋅ , × 
Divided sign  : , ÷ , / 
Plus minus sign  ± , ∓ 
Comparison sign  < , ≤ , = , ≥ , > 
Root sign  √ 
Percent sign  % 
Analysis  
Sum symbol  Σ 
Product mark  Π 
Difference sign , Nabla  ∆ , ∇ 
Prime  ′ 
Partial differential  ∂ 
Integral sign  ∫ 
Concatenation characters  ∘ 
Infinity symbol  ∞ 
geometry  
Angle sign  ∠ , ∡ , ∢ , ∟ 
Vertical , parallel  ⊥ , ∥ 
Triangle , square  △ , □ 
Diameter sign  ⌀ 
Set theory  
Union , cut  ∪ , ∩ 
Difference , complement  ∖ , ∁ 
Element character  ∈ 
Subset , superset  ⊂ , ⊆ , ⊇ , ⊃ 
Empty set  ∅ 
logic  
Follow arrow  ⇒ , ⇔ , ⇐ 
Universal quantifier  ∀ 
Existential quantifier  ∃ 
Conjunction , disjunction  ∧ , ∨ 
Negation sign  ¬ 
In mathematics , formal logic and in the exact natural sciences , the equal sign ( = , also called isequal sign ) stands between two expressions with the same value .
history
In ancient and medieval mathematics, the equality of two expressions was still literally written down (e.g. est egale for "is equal"). Descartes (1596–1650) shortened this with a æ (for Latin aequalis ) rotated by 180 ° , with the horizontal line being more and more omitted in the subsequent period. This symbol survived in the form ∝ as one of the proportionality symbols . As the founder of modern equal sign the Welsh mathematician applies Robert Recorde (15101558) with his book The Whetstone of Witte , dt (1557). The whetstone of knowledge . He justified the two parallel lines for an equality symbol with the early New English sentence … bicause noe.2.thynges, can be moare equalle. (Today's English: because no two things can be more equal , " because no two things can be the same").
The =, which was already used in England , was probably first introduced on the European continent by Gottfried Wilhelm Leibniz (1646–1716).
presentation
The equal sign is coded in ASCII with 61 ( decimal ), so as Unicode U + 003D (61 decimal = 3D hexadecimal ). It is not one of the named entities in markup languages , but can be replaced with =
or in HTML =
.
use
General use
The glyph =
is generally used to represent facts of correspondence, equality or identity , in mathematics, computer science and technology also the assignment in the sense of a subsequent equal use.
The equal sign is often used as a substitute for the double hyphen ⹀ (U + 2E40) or its Japanese variant (U + 30A0).
In electrical engineering , the equal sign is used to identify direct voltage .
The equal sign and its variations
There are also modified forms with a different meaning, such as B. the equivalent sign (≙) or the rounding sign ( ≈) with the meaning approximately equal / rounded . If the inequality of two numbers is to be shown, a crossed out equal sign (≠) is used. A shape with three horizontal bars (≡) is used to indicate the identity of two arithmetic expressions.
The modifications: = or =: are used in mathematics to represent a definition of one side by the other side. The colons are always next to the object to be defined. The ≡ previously used for this should no longer be used in this sense ( DIN 1302 ), but shapes such as (DIN 1302) or ( ISO 31 11) are possible.
For example, the set A can be defined as follows:
In programming languages that are derived from C , the (simple) equal sign is used for value assignment . In these languages, however, a double equal sign ( == ) is usually used as the comparison operator . In Fortran is used for the comparison operator. In languages of the Pascal family, on the other hand, a: = is used for the assignment (in the predecessor Algol 60 this character combination or also a "←") and the equal sign as a comparison operator. There are also languages such as B. BASIC , in which it is always clear from the context whether it is an assignment or a comparison and therefore use the equal sign for both the assignment and the comparison operator.
.EQ.
Inequality sign
Since the character for inequality ≠ is not available in the ASCII character set, various programming languages use digraphs such as <>
(Pascal, BASIC), /=
(Ada), !=
( not equal , C, C ++) or ~=
(ML); Fortran used .NE.
(because of English n ot e qual , not equal ).
Z.  Unicode  meaning  description  Z.  Unicode  meaning  description  

=  U+003D 
equal  ≠  U+2260 
unequal; not equal ^{(1)}  
≡  U+2261 
congruent , identical  ≢  U+2262 
not congruent ^{(1)}  
≐  U+2250 
Limit value approximation  
≃  U+2243 
asymptotically equal  ≄  U+2244 
asymptotically unequal ^{(1)}  
≂  U+2242 
Minus tildes  
≅  U+2245 
approximately equal (AngloAmerican, according to DIN only permissible for asymptotically equal (≃)) 
≆  U+2246 
roughly, but not exactly the same  
≇  U+2247 
neither roughly nor exactly the same  
isomorphic , isomorphic in terms of category theory  
≊  U+224A 
about the same or equal  
≈  U+2248 
roughly equal / rounded ( coll .: almost equal )  Double tilde  ≉  U+2249 
not about the same (coll .: not almost the same )  Crossed out double tildes  
≋  U+224B 
Triple tilde  
≗  U+2257 
about the same  
≒  U+2252 
roughly the same or picture  ≓  U+2253 
Picture or about the same  
≌  U+224C 
all the same  
≍  U+224D 
equivalent to  
≣  U+2263 
exactly equivalent  
≎  U+224E 
geometrically equivalent  
≏  U+224F 
Difference between  
≑  U+2251 
geometrically the same  
≚  U+225A 
equiangular  
≔  U+2254 
results from (for definition on the left (: =) not provided)  ≕  U+2255 
does not result from (for definition on the right (= :) not provided)  
≜  U+225C 
right by definition  
≝  U+225D 

Definition on the left  Colon + equal sign  Righthand definition  Equal sign + colon  
should be the same (for example in the introduction of evidence )  
≙  U+2259 
corresponds  
≘  U+2258 
corresponds to (unusual)  
≞  U+225E 
measured  
≟  U+225F 
maybe right away  
≛  U+225B 
Star is the same  
≖  U+2256 
Circle in equal sign 
 ^{(1)} DIN 1302prescribes vertical strikethrough, but allows oblique strikethrough "if it is necessary for reasons of composition technology". ISO 31generally allows both forms.
See also
Individual evidence
 ↑ ... and written “is equal sign”; see also in the DWDS , under the equal sign , there also with "actual equal sign" (accessed on November 15, 2018)
 ^ Robert Recorde : The Whetstone of Witte . London 1557, p. 238.
 ↑ Matthias Helle: = . In: FU Berlin, Institute for Computer Science (Ed.): Seminar History of Mathematical Notation . 1999 (fuberlin.de; script for the lecture on July 21, 1999).
 ↑ ^{a } ^{b} Hans Friedrich Ebel , Claus Bliefert , Walter Greulich : Writing and publishing in the natural sciences . WileyVCH, 2006, ISBN 9783527308026 , 6.5.4 Frequently occurring special characters , p. 352 ff . ( limited preview in Google Book search).