Open Real Interval/Examples/Example 1
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Example of Open Real Interval
Let $I$ be the open real interval defined as:
- $I := \openint 1 2$
Then $3 \notin I$.
Proof
By definition of open real interval:
- $I = \set {x \in \R: 1 < x < 2}$
As $3 > 2$ it follows that $3 \notin I$.
$\blacksquare$
Sources
- 1977: K.G. Binmore: Mathematical Analysis: A Straightforward Approach ... (previous) ... (next): $\S 2$: Continuum Property: Exercise: $\S 2.10 \ (1) \ \text{(i)}$