Solution
= Solution
A subset of $\mathbb R$ is a <Borel set> when it belongs to the <Borel sigma-algebra>, the smallest <sigma-algebra> containing every <open set> of $\mathbb R$.
= Solution
A subset of $\mathbb R$ is a <Borel set> when it belongs to the <Borel sigma-algebra>, the smallest <sigma-algebra> containing every <open set> of $\mathbb R$.