Theorem 6.2. Let C be a compact subset of Rstd- Then C has a maximum point, that is, there is a point m E C such that for every x E C, x < m.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
icon
Related questions
Topic Video
Question
100%

How do I show 6.2? Could you explain it in detail?

**Definitions and Theorem on Covers and Compactness**

**Definition.** Let \( A \) be a subset of \( X \) and let \( \mathcal{C} = \{C_\alpha\}_{\alpha \in \lambda} \) be a collection of subsets of \( X \). Then \( \mathcal{C} \) is a **cover** of \( A \) if and only if \( A \subseteq \bigcup_{\alpha \in \lambda} C_\alpha \). The collection \( \mathcal{C} \) is an **open cover** of \( A \) if and only if \( \mathcal{C} \) is a cover of \( A \) and each \( C_\alpha \) is open. A **subcover** \( \mathcal{C}' \) of a cover \( \mathcal{C} \) of \( A \) is a subcollection of \( \mathcal{C} \) whose elements form a cover of \( A \).

For instance, the open sets \(\{(-n,n)\}_{n \in \mathbb{N}}\) form an open cover of \( \mathbb{R} \). A subcover of this cover is \(\{(-n,n)\}_{n \geq 5}\), because these sets still cover all of \( \mathbb{R} \).

**Definition.** A space \( X \) is **compact** if and only if every open cover of \( X \) has a finite subcover.

**Theorem 6.2.** Let \( C \) be a compact subset of \( \mathbb{R}_{\text{std}} \). Then \( C \) has a maximum point, that is, there is a point \( m \in C \) such that for every \( x \in C \), \( x \leq m \).
Transcribed Image Text:**Definitions and Theorem on Covers and Compactness** **Definition.** Let \( A \) be a subset of \( X \) and let \( \mathcal{C} = \{C_\alpha\}_{\alpha \in \lambda} \) be a collection of subsets of \( X \). Then \( \mathcal{C} \) is a **cover** of \( A \) if and only if \( A \subseteq \bigcup_{\alpha \in \lambda} C_\alpha \). The collection \( \mathcal{C} \) is an **open cover** of \( A \) if and only if \( \mathcal{C} \) is a cover of \( A \) and each \( C_\alpha \) is open. A **subcover** \( \mathcal{C}' \) of a cover \( \mathcal{C} \) of \( A \) is a subcollection of \( \mathcal{C} \) whose elements form a cover of \( A \). For instance, the open sets \(\{(-n,n)\}_{n \in \mathbb{N}}\) form an open cover of \( \mathbb{R} \). A subcover of this cover is \(\{(-n,n)\}_{n \geq 5}\), because these sets still cover all of \( \mathbb{R} \). **Definition.** A space \( X \) is **compact** if and only if every open cover of \( X \) has a finite subcover. **Theorem 6.2.** Let \( C \) be a compact subset of \( \mathbb{R}_{\text{std}} \). Then \( C \) has a maximum point, that is, there is a point \( m \in C \) such that for every \( x \in C \), \( x \leq m \).
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 3 steps with 4 images

Blurred answer
Knowledge Booster
Propositional Calculus
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, advanced-math and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Advanced Engineering Mathematics
Advanced Engineering Mathematics
Advanced Math
ISBN:
9780470458365
Author:
Erwin Kreyszig
Publisher:
Wiley, John & Sons, Incorporated
Numerical Methods for Engineers
Numerical Methods for Engineers
Advanced Math
ISBN:
9780073397924
Author:
Steven C. Chapra Dr., Raymond P. Canale
Publisher:
McGraw-Hill Education
Introductory Mathematics for Engineering Applicat…
Introductory Mathematics for Engineering Applicat…
Advanced Math
ISBN:
9781118141809
Author:
Nathan Klingbeil
Publisher:
WILEY
Mathematics For Machine Technology
Mathematics For Machine Technology
Advanced Math
ISBN:
9781337798310
Author:
Peterson, John.
Publisher:
Cengage Learning,
Basic Technical Mathematics
Basic Technical Mathematics
Advanced Math
ISBN:
9780134437705
Author:
Washington
Publisher:
PEARSON
Topology
Topology
Advanced Math
ISBN:
9780134689517
Author:
Munkres, James R.
Publisher:
Pearson,