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What does this answer mean? (continuous functions)

  1. Feb 24, 2013 #1
    Working on some problems that have vectors, for example

    f(x) = [-x1/|X|3, -x2/|X|3]

    And then I am asked to find the largest interval of existence. The answer says "E = R2 ~ {0}.

    I'm not sure what this means. Does it mean the interval of existence is everywhere except 0? Is that what the ~ {0} means? It seems like the answer is that any x1, x2 value in R2 space satisfies continuity, but then I have no idea where the ~{0} comes from.
    Last edited: Feb 24, 2013
  2. jcsd
  3. Feb 24, 2013 #2


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    Yes, given the context I'm sure it means "every point in ##\mathbb{R}^2## except the origin. A more standard notation would be ##\mathbb{R}^2 \setminus \{(0,0)\}##. By the way, this set isn't an interval at all.

    The reason ##(0,0)## is excluded is because your function is not even defined there because of the ##|x|^3## in the denominator.
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