Thread: open and closed

consider (ℝ,τ) , where τ={∅}∪{u⊆ℝ:{-π,π}⊆u}.
Is [-4.4] open in (ℝ,τ) ? Justify your answer
Is (-3,3) closed in (ℝ,τ) ? Justify your answer

Originally Posted by blbl

consider (ℝ,τ) , where τ={∅}∪{u⊆ℝ:{-π,π}⊆u}.
Is [-4.4] open in (ℝ,τ) ? Justify your answer
Is (-3,3) closed in (ℝ,τ) ? Justify your answer

This is pretty clearly a homework or test problem from an iintroductory class in point-set topology.

We will not do your schoolwork for you. That would be cheating.