World Library  
Flag as Inappropriate
Email this Article

One half

Article Id: WHEBN0000464963
Reproduction Date:

Title: One half  
Author: World Heritage Encyclopedia
Language: English
Subject: WikiProject Numbers, 1/2, 50%, Half (disambiguation), BD+
Publisher: World Heritage Encyclopedia

One half

One half
prefixes hemi- (from Greek)

semi-/demi- (from Latin)

Binary 0.1 or 0.011111111111...
Decimal 0.5 or 0.499999999999...
Duodecimal 0.6 or 0.5BBBBBBBBBBBB...
Hexadecimal 0.8 or 0.7FFFFFFFFFFF...
Continued fraction [0; 1, 1] or [0; 2]

floating point

3F000000 (hex) =


One half is the irreducible fraction resulting from dividing one by two (½), or the fraction resulting from dividing any number by its double. Multiplication by one half is equivalent to division by two, or halving; conversely, division by one half is equivalent to multiplication by two, or "doubling". One half appears often in mathematical equations, recipes, measurements, etc. Half can also be said to be one part of something divided into two equal parts.

For instance, the area S of a triangle is computed

S = ½ × base × perpendicular height.

One half also figures in the formula for calculating figurate numbers, such as triangular numbers and pentagonal numbers:

½ × n [(s - 2) n - (4 - s)]

and in the formula for computing magic constants for magic squares

M2(n) = ½ × [n (n2 + 1 )].

The Riemann hypothesis states that every nontrivial complex root of the Riemann zeta function has a real part equal to ½.

One half has two different decimal expansions, the familiar 0.5 and the recurring 0.49999999... It has a similar pair of expansions in any even base. It is a common trap to believe these expressions represent distinct numbers: see the proof that 0.999... equals 1 for detailed discussion of a related case.

Particularities in writing and language

Postal stamp, Ireland, 1940: one halfpenny postage due.

½ is also one of the few fractions to usually have a key of its own on typewriters (see fractions). It also has its own point in some early extensions of ASCII at 171; and in Unicode, it has its own code point at U+00BD (decimal 189) in the C1 Controls and Latin-1 Supplement block, and a cross-reference in the Number Forms block, which contains some other fractions.

One half is also one of the few fractions which is commonly expressed in natural languages by suppletion rather than regular derivation; compare English one half with regular formations like one sixth from six.

See also

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.