Describe the partition for the equivalence relation T

needhelp83
Messages
193
Reaction score
0
For the set A = {1,2,3,4,5,6,7}, determine whether script A is a partition of A. script A = {{1,3,},{5,6}, {2,4},{7}}

Describe the partition for the equivalence relation T defined for x,y \in \mathbbc{R} by X T y iff \left[ \left[x \right] \right] = \left[ \left[y \right] \right] where \left[ \left[x \right] \right] is definied to be the greatest integer iin x (the largest integer n such that n \leq x).

Can anyone help me with this partition stuff. It would be very appreciated. :)
 
Physics news on Phys.org


Can you start by giving the definition of a partition?
Then try to check if the given sets A, \mathcal{A} satisfy this definition.

For the second one, can you imagine what the equivalence classes look like?
 


(i) If X \in \mathcal{A}, then X \neq \o
(ii) If X \in \mathcal{A} and Y \in \mathcal{A}, then X=Y or X \cap Y= \o
(iii)\bigcup_{X \in \mathal{A}}X=A

I found this to be a definition for an equivalence class:
In mathematics, given a set X and an equivalence relation ~ on X, the equivalence class of an element a in X is the subset of all elements in X which are equivalent to a:

\left[a\right]={x \in X|x \sim a}
 


needhelp83 said:
(i) If X \in \mathcal{A}, then X \neq \o
(ii) If X \in \mathcal{A} and Y \in \mathcal{A}, then X=Y or X \cap Y= \o
(iii)\bigcup_{X \in \mathal{A}}X=A
That's long winded! A "partition" of a set, A, is a collection of subsets of A such that every member of A is in one and only one of the subsets. Here, the members of A are 1, 2, 3, 4, 5, 6, 7. Is every one of those numbers in one of the given subsets? Is any number in more than one?

I found this to be a definition for an equivalence class:
In mathematics, given a set X and an equivalence relation ~ on X, the equivalence class of an element a in X is the subset of all elements in X which are equivalent to a:

\left[a\right]={x \in X|x \sim a}

Okay, and the relation x T y is defined by "x T y if and only if the largest integer less than or equal to x is the same as the largest integer less than or equal to y".

Now try some examples. What numbers are equivalent to 0? to 1/2? to 5/4? to \pi?
 


All the numbers in a subset are only in one subset once.

-What do you mean by what numbers are equivalent to 0, 1/2, pi, etc
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top