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Homework Help: What do these wierd square brackets mean? [| |]

  1. Jul 23, 2011 #1
    What do these wierd square brackets mean??? [| |]

    1. The problem statement, all variables and given/known data
    In my BC Calc summer homework (taking the course next school year), I came across these odd square brackets in a limit problem and have no clue what they mean. I've looked all over the internet and cannot find anything similar. They're like [] but have two vertical lines on each bracket instead of the just one.

    this is the best representation I can give:
    [| x - 1|]

    The problem is this:
    lim [| x - 1 |]
    x -> 4

    2. Relevant equations

    3. The attempt at a solution
    For now I just kind of ignored the brackets and just plugged in 4 for x and got 3.

    Please help! I am thoroughly confused and extensively frustrated. >=(
  2. jcsd
  3. Jul 23, 2011 #2
    Re: What do these wierd square brackets mean??? [| |]

    the inside bars stand for the absolute value function. the outer brackets stand for the floor function I guess. I hope I understood your post correctly.
    Last edited: Jul 23, 2011
  4. Jul 23, 2011 #3
    Re: What do these wierd square brackets mean??? [| |]

    I think these brackets ( [ ] ) represent greatest integer function. [x] means greatest integer less than equal to x. In all the question that i have faced if it ( [ ] ) represent greatest integer function then it is mentioned in the question. Is it mentioned in your case ?

    and | | modulas function. You need to learn this from book. And i am sure that it is modulas function
    You need to learn about these two function before doing question.
    I am not sure that [ ] represent greatest integer function if it is not mentioned.

    what is answer it that limit does not exist.todays I am also learning limits.
    Last edited: Jul 23, 2011
  5. Jul 23, 2011 #4


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    Re: What do these wierd square brackets mean??? [| |]

    Did they look more like ⟦ and ⟧ ? (I super-sized them for clarity.)

    Added in Edit:

    Assuming that the symbols ( ⟦ , ⟧ ) are correct, they are used to represent the greatest integer function, also known as the 'floor function'. See this http://www.mathwords.com/f/floor_function.htm" [Broken].

    I suspect that there is no absolute value involved at all, simply the floor function.
    Last edited by a moderator: May 5, 2017
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