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Homework Help: Quick question about two sets...

  1. Dec 6, 2017 #1
    1. The problem statement, all variables and given/known data
    Is the set (r,-r,0) the same as the set (-r,r,0)

    Sorry I need to know the answer to this right now, somebody in class confused me and I can't talk to my teacher right now.

    My answer: yes it is the same set. Can anyone just give me a quick yes/no?

    2. Relevant equations


    3. The attempt at a solution
     
  2. jcsd
  3. Dec 6, 2017 #2

    BvU

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    I have to brake for a car in front of me, so I can't answer 'it depends' right now ! :rolleyes:

    good luck with your test !
     
  4. Dec 6, 2017 #3

    Mark44

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    Yes, as sets they are the same. Order doesn't matter here.
     
  5. Dec 6, 2017 #4

    BvU

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    I wasn't really in a car, but safely behind my desktop. Just didn't want to interfere in a testing situation :rolleyes:

    If the order of elements in a set matters, we call it a sequence. (You need a sequence of instructions when asking directions; with a set you wouldn't know what to do first)

    A set is a collection. Two collections are the same if they contain the same elements. Yours do
     
  6. Dec 6, 2017 #5

    Ray Vickson

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    Your notation is poor: in Mathematics, we almost always denote sets using curly brackets, like this: ##\{ r, -r,0 \}##, and in that case, order does not matter: ##\{ r,-r,0 \} = \{ r,-r,0 \} = \{ r,0,-r \} = \{ -r,0,r \} = \{ 0,r,-r \} = \{ 0,-r,r \}. ## Other types of brackets like ( , ) , [ , ] or < , > denote objects like lists, vectors, arrays, sequences, etc., and for all of them order is crucial.
     
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