# Math Help - open and closed

1. ## 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

2. 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 starting to get ridiculous. What do you think??? You still haven't responded as to what you really mean by this specific topology!