Results Concerning Limits of Sequences of Intervals
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Decreasing Sequences of Sets
Limit of Decreasing Sequence of Unbounded Below Closed Intervals with Endpoint Tending to Negative Infinity
Let $\sequence {x_n}_{n \mathop \in \N}$ be a decreasing sequence with $x_n \to -\infty$.
Then:
- $\ds \bigcap_{n \mathop = 1}^\infty \hointl {-\infty} {x_n} = \O$
That is:
- $\hointl {-\infty} {x_n} \downarrow \O$
where $\downarrow$ denotes the limit of decreasing sequence of sets.
Limit of Decreasing Sequence of Unbounded Below Closed Intervals
Let $x \in \R$.
Let $\sequence {x_n}_{n \mathop \in \N}$ be a decreasing sequence converging to $x$.
Then:
- $\ds \bigcap_{n \mathop = 1}^\infty \hointl {-\infty} {x_n} = \hointl {-\infty} x$
That is:
- $\hointl {-\infty} {x_n} \downarrow \hointl {-\infty} x$
where $\downarrow$ denotes the limit of decreasing sequence of sets.
Limit of Decreasing Sequence of Left Half-Open Intervals with Lower Bound Converging to Upper Bound
Let $a, b \in \R$ have $a < b$.
Let $\sequence {a_n}_{n \mathop \in \N}$ be an increasing sequence with $a_n \to b$.
Then we have:
- $\ds \bigcap_{n \mathop = 1}^\infty \hointl {a_n} b = \set b$
That is:
- $\hointl {a_n} b \downarrow \set b$
where $\downarrow$ denotes the limit of decreasing sequence of sets.