Thread: Interior, Closure and Boundary of sets

A little topology (I think) problem here:

For A:= [0,1) ∪ ([2,3] ∩ ) ∪ {5} ⊂ R (real numbers) find the closure, boundary and interior of A

I know the definitions but I don't know how to actually calculate them

To compute the closure, just notice that the closure of a finite union is the union of the closures.
For the interior, can the points of be in it? And what about ?

Originally Posted by fylth

For A:= [0,1) ∪ ([2,3] ∩ ) ∪ {5} ⊂ R (real numbers) find the closure, boundary and interior of A

Do you know that

The boundary is the closure toss (set difference) the set...
The interior is...