Definizione
145
[07D] Dati \(x,z∈ X\) si definiscono i seguenti intervalli standard
\[ \begin{aligned} (x,z)& =& \{ y∈ X: x{\lt}y{\lt}z \} \\ {} (x,z]& =& \{ y∈ X: x{\lt}y≤ z \} \\ {} (x,∞)& =& \{ y∈ X: x{\lt}y \} \\ {} [x,z)& =& \{ y∈ X: x≤ y{\lt}z \} \\ {} [x,z]& =& \{ y∈ X: x≤ y≤ z \} \\ {} [x,∞)& =& \{ y∈ X: x≤ y \} \\ {} (-∞,z)& =& \{ y∈ X: y{\lt} z \} \\ {} (-∞,z]& =& \{ y∈ X: y≤ z \} \\ {} (-∞,∞)& =& X~ ~ . \end{aligned} \]