|
Size: 573
Comment:
|
Size: 574
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 1: | Line 1: |
| A set ''E'' is ''compact'' if and only if, for every family [[latex2($\{G_{ \alpha } \}_{\alpha \in A}$)]] of open sets such that [[latex2($E \subset \cup_{\alpha \in A}G_{\alpha}$)]] | A set ''E'' is ''compact'' if and only if, for every family [[latex2($\{G_{ \alpha } \}_{\alpha \in A}$)]] of open sets such that [[latex2($E \subset \cup_{\alpha \in A}G_{\alpha}$)]] |
A set E is compact if and only if, for every family latex2($\{G_{ \alpha } \}_{\alpha \in A}$) of open sets such that latex2($E \subset \cup_{\alpha \in A}G_{\alpha}$)
Heine-Borel Theorom: A set latex2(\usepackage{amsfonts} % $E \subset \mathbb{R}$) is compact iff E is closed and bounded.
Example [2,8] is a compact set. The unit disk including the boundary is a compact set. (3,5] is not a compact set. Note that all of these examples are of sets that are uncountably infinite.
Introduction to Analysis 5th edition by Edward D. Gaughan