章魚
Lv 7
章魚 asked in 科學及數學數學 · 1 decade ago

k ∈N = 自然數???

k∈N 是解k是自然數???

另外還有什麼例子是k∈sth

4 Answers

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  • 1 decade ago
    Favorite Answer

    My dear cousin

    Seems that you are not familar to Set theory

    Let me introduce you this topic

    A set can be interpreted as a bag containing some objects

    These objects are called "the elements" of the set.

    e.g. Let S be the set of atoms in the whole world, then every single atom is an element of S.

    Back to your question,

    mathematicians use spectial symbols (N, I, Q, R and C) to show the set of Natural no.s, intergers, Rational no.s, Real no.s and complex no.s.

    The expression " a ∈S " means " a is an element of the set S".

    Therefore,

    k ∈N means k is a natural no.

    k ∈I means k is an integer

    k ∈Q means k is a rational no.

    k ∈R means k is a real no.

    k ∈C means k is a complex no.

    ect.

    If you are interested in Set theory, you may read the book "Stories about Sets (集的故事)", it is a very good book to beginners.

    At last, I would like to conclude with 2 question

    i )Do the set N has less elements than that in I?

    ii)Do the set I has less elements than that in Q?

    The answer of this two questions can be found in the book mentioned above.

  • kc
    Lv 5
    1 decade ago

    May be you could have some ideas from the following web site:

    http://zh.wikipedia.org/w/index.php?title=Zermelo_...

  • ip
    Lv 7
    1 decade ago

    WOW~!@@

  • 1 decade ago

    k∈R:k係實數

    Source(s): me
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