## windsylph Group Title Discrete Math: Union from i = 1 to infinity of A_i where A_i = (0,i), that is, the set of real numbers x such that 0 < x < i? I answered {x in R | 0 < x < infinity} but I'm worried about the correctness of that answer, since wouldn't this apply if A_i = (0,i] also? 2 years ago 2 years ago

1. satellite73 Group Title

first answer was right, but you don't need to write the $$\infty$$ on the right

2. KingGeorge Group Title

$\bigcup_{i=1}^\infty A_i \quad \text{where}\quad A_i=(0, i)$I'm going to agree with @satellite73 here. I see nothing wrong with your answer. And it would be the same if $$A_i=(0, i]$$. It's just a different way of writing things.

3. windsylph Group Title

Thank you very much.