Plus-minus sign

The plus minus sign ( ±) and the minus plus sign ( ∓ ) are characters from mathematics. With them may be expressed on the one hand, that a term in a mathematical expression can be either positive or negative ( it means " ± 5 " means that the number can be looked at 5 or -5). Secondly, with the number of preceding plus minus sign, the entire area enclosed by the positive and negative value of the number range of numbers are called ( so called " ± 5", from -5 to 5, including these values ​​themselves ).

Typography

The plus minus sign usually consists of the unchanged form of the plus sign from the same font with a arranged below minus sign, which has the same shape as the horizontal bars of the plus sign. In most cases, a gap is left between the components, which is less than the line width; There you will also find forms at which touch the components. At minus plus sign, the minus sign is placed in the same way on the plus sign. The vertical position of characters in the typographic line system is inconsistent.

Use

Technology and merchant beings

In technology, the plus minus sign denotes uncertainties or tolerances. For example, " 5 cm ± 0.05 cm " means that the actual length between the values ​​should be 4.95 cm and 5.05 cm.

Similarly, can be expressed in Kaufmann nature that one thing is vitiated by an error when the value of a measurable quantity (eg length, weight) is outside the range as indicated.

Mathematics

Formularies

Often the two characters are used in formularies to combine space-saving two similar formulas. This is illustrated here by the example of the formulas from the addition theorems of trigonometry. In compact notation are the two formulas

Square root

Frequent application is the plus minus sign at the root extraction (pulling the root). Because, for example, is both, and is, to write. The equation therefore has the two real numbers and as a solution. As a shorthand notation to write it.

Chemistry

In chemistry - particularly in stereochemistry - the plus minus sign is used as a prefix for the identification of racemates, which are 1:1 mixtures of two enantiomers, of which rotates a plane of polarized light in the polarimeter to the right and the other to the left.

Physics

In physics and related sciences (eg, astronomy) the plus minus sign is used for indication of the uncertainties, such as test results and other size. Indicated is mostly the standard deviation. This is then stated as the context that 68 % of all measured values ​​are within the specified interval, or that the said value for said quantity with a probability of 68 % in the specified interval ( the trust region).

Chess

Commenting on a chess game both characters denote a position evaluation:

Representation in computer systems

In the ASCII character set from 1963 the plus minus sign is not included, which is why many older computer systems it could not represent. However, it was (also known as Latin-1) included 1986 already in the ASCII extension ISO 8859-1. Almost all modern computers use the measures introduced in 1991, the Unicode standard and can therefore be easily processed and are both characters.

If you want to enter the plus minus sign on Microsoft Windows, you hold the Alt key and typing on the number pad " 0177 " one. On Unix systems (such as Linux), the plus minus sign can often by pressing the Compose key followed by followed by - generate.

• Mathematical signs
• Addition
• Subtraction