Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quotien Set

  1. Jun 3, 2008 #1
    I have a question.....
    "Is the quotient set of a set S relative to a equivalence relation on S a subset of S?"
    I suppose "no",since the each member of the quotient set is a subset of S and consequently it is a subset of the power set of S,but I have e book saying that "yes",I am a bit confused,can any one ensure me??????
  2. jcsd
  3. Jun 3, 2008 #2


    User Avatar
    Science Advisor

    No, the quotient set of set S, relative to some equivalence relation on S, is not a subset of S. It is the set of all equivalence classes defined by the relation and so, as you say, a subset of the power set of S. We could, by choosing one "representative" of each equivalence class, "identify" the quotient set with a subset of S but that can be done in many different ways depending on the choices of "representative".

    For example, if S= N, the natural numbers, and the relation is xRy if and only if x-y is a multiple of 3, then the quotient set is the set containing: the multiples of 3, the set of numbers of the form 3n+1, and the set of numbers of the form 3n+2. We can, and often do identify those with {0, 1, 2}. But we could as easily identify them with {3, 4, 5}, etc.
  4. Jun 3, 2008 #3
    Thank u very much,I am complete agree with u.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook