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What's the real number sign with a + under it?

  1. Apr 9, 2012 #1
    1. The problem statement, all variables and given/known data
    What does the real number sign with a + under it mean? Check the example below.

    2. Relevant equations
    http://upload.wikimedia.org/wikibooks/en/math/8/d/3/8d380fa4b673b84ddb613bed8ab8f189.png [Broken]


    3. The attempt at a solution
    Tried Googling, but didn't find anything.
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Apr 9, 2012 #2
    I've never seen this notation, but i'd say it means the positive real numbers.
     
  4. Apr 9, 2012 #3
  5. Apr 9, 2012 #4

    Office_Shredder

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    It typically means positive real numbers, or occasionally non-negative real numbers depending on the context and how lazy the author is
     
  6. Apr 9, 2012 #5
    Just to mention it... normally you find it (I found it...) as a power rather than as a subscript!
     
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