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

[Cinitiator]

Homework Statement

What does the real number sign with a + under it mean? Check the example below.

Homework Equations

http://upload.wikimedia.org/wikibooks/en/math/8/d/3/8d380fa4b673b84ddb613bed8ab8f189.png

The Attempt at a Solution

Tried Googling, but didn't find anything.

 

[mtayab1994]

I've never seen this notation, but i'd say it means the positive real numbers.

 

[mtayab1994]

take a look at this http://en.wikibooks.org/wiki/Macroeconomics/Optimal_Growth

 

[Office_Shredder]

It typically means positive real numbers, or occasionally non-negative real numbers depending on the context and how lazy the author is

 

[Brais]

Just to mention it... normally you find it (I found it...) as a power rather than as a subscript!