Question

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?

Answer 1

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

Answer 2

\[\bigcup_{i=1}^\infty A_i \quad \text{where}\quad A_i=(0, i)\]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.

Answer 3

Thank you very much.