1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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

    Staff: Mentor

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

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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

    User Avatar
    Science Advisor
    Homework Helper

    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.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Quick question about two sets...
Loading...