# Homework Help: Closed Sets

1. Oct 19, 2005

### Virtate

How do you do this proof??? Isn't it already obvious given the definition? I have no idea how to go about writing it down. If someone could help me with this, I would really appreciate it. Thanks :) Sorry I had to write it in such a messy way.

Define the closure of A as A closure = (x|for every open rectangle u containing x, intersection of u and A not equal to 0)

a) Show that A closure = A union bdA

b) Prove that bdA = intersection of A closure and (R^n-A) closure = bd(R^n-A)

Last edited: Oct 20, 2005
2. Oct 19, 2005

### Tom Mattson

Staff Emeritus