I was just wondering that one can easily check the presence of any number rational/irrational in $\mathbb R$ but I could not find if Mathematica supports any notation for open sets. The number of elements in $\mathbb R$ or open sets will be infinite and anyway $\mathbb R$ itself is infinite open set. So, I wanted to know
- What is the algorithm that can be used to check for the presence of a number in $\mathbb R$ ?
- How can one pick out one subset of $\mathbb R$ as some $(a,b)$ or $[a,b]$ and work with it ?
Any help is appreciated. Thanks.