# Relations math concepts

1. Apr 14, 2005

### liahow

Not really understanding these concepts.

Consider the following relation on the set of all circles in the xy plane: A ~ B if and only if the center of circle A is inside circle B. Is ~ reflexive? Is ~ symmetric? Is ~ antisymmetric? Is ~ transitive? Prove answers.

Consider the following relation on the set of all recurrence relations. X ~ D if and only if all of the terms of the sequence associated with D appear in the sequence associated with X. Is ~ reflexive, symmetric, antisymmetric, transitive? Prove.

Last edited: Apr 14, 2005
2. Apr 14, 2005

### hypermorphism

What have you done so far ? Do you understand the definitions ?

3. Apr 14, 2005

### liahow

As far as the definitions go, what we learned in our books is different from this equation. We've been given sets and told to go with those. Perhaps it's just my own ignorance, but when a problem is so dramatically phrased differently than the way I learn it, I am stuck in neutral.

4. Apr 14, 2005

### hypermorphism

Let's look at this one. Rephrase the abstract property "symmetric" in terms of the set you are working with. In this case, it is asking "If a circle A has its center inside circle B, does it necessarily follow that circle B has its center inside circle A ?"
Do this with the rest of the questions.

Last edited: Apr 15, 2005
5. Apr 15, 2005

### honestrosewater

Just so liahow isn't confused, the question above is for the symmetric property. A ~ B if and only if the center of circle A is inside circle B, so reflexive would just be A ~ A, or "the center of circle A is inside circle A".

6. Apr 15, 2005

### HallsofIvy

You were asked "what is the definition" of a relation. Please tell us what definitions you have learned, whether they are "different from this equation" or not (I don't quite understand that- you haven't cited any equations).