The relationship between an equivalence relation, equivalence classes, and partitions?

504 Views Asked by At

So I'm struggling right now to understand the concepts behind equivalence relations, equivalence classes, and partitions.

This is what I understand about all these topics right now:

Equivalence Relations: A relation is said to be equivalent if the relation is:

  1. Symmetric, where xRy implies yRx

  2. Transitive, where xRy ^ yRz implies that xRz.

  3. Reflexive, where if x belongs to the real set of numbers, xRx.

Equivalence Classes If we have a equivalence relation represented by ~ on the Set A, where x ∈ A, then we have:

Ex ={y ∈ A:x∼y}, which is a way to represent an equivalence class of x. (What exactly does this mean? Does this mean that x is an equivalence relation of y, and that y belongs to the subset A? Not understanding this, I also don't know how to determine the equivalence class if I've determined that a certain relation is an equivalence relation.)

Partitions A set is said to be a partition if it satisfies the following:

Say we have a Set A, and it has a either finite or infinite amount of subsets B.

The union of all the subsets B should be the set A.

The subsets of B should be disjoint.

Can someone fill in the holes of my understanding? (Some are in italics, also correct any of my understanding if possible)