Chapter 5: Problem 33
Let \(U=\\{x | x \text { is a natural number and } 1 \leq x \leq 12\\}\) \(A=\\{1,2,3,4,5\\}, B=\\{2,4,6,8,10\\}\) and \(C=\\{3,6,9,12\\} .\) Determine the cardinality of the indicated sets. $$B^{C}$$
Short Answer
Expert verified
The cardinality of \( B^c \) is 7.
Step by step solution
01
Determine the Universal Set
The universal set \( U \) is given by \( U = \{ x | x \text{ is a natural number and } 1 \leq x \leq 12 \} \). This means \( U = \{ 1, 2, 3, ..., 12 \} \).
02
Identify Elements in Set B
The set \( B = \{ 2, 4, 6, 8, 10 \} \) includes the even natural numbers between 1 and 12.
03
Complement of Set B in U
\( B^c \) refers to the complement of set \( B \) with respect to the universal set \( U \). This means we list all elements in \( U \) that are not in \( B \).
04
Calculate B^C
Since \( B = \{ 2, 4, 6, 8, 10 \} \), then \( B^c = \{ 1, 3, 5, 7, 9, 11, 12 \} \), which are all elements in \( U \) not present in \( B \).
05
Determine the Cardinality of B^C
Count the elements in \( B^c \). We have \( B^c = \{ 1, 3, 5, 7, 9, 11, 12 \} \), which contains 7 elements. Thus, the cardinality of \( B^c \) is 7.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Universal Set
The concept of a universal set is fundamental in set theory. A universal set contains all possible elements under consideration for a particular discussion or problem. In our exercise, the universal set \( U \) is defined as all natural numbers between 1 and 12:
- This means \( U = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12\} \).
Set Complement
The complement of a set is an important idea in set theory, denoted as \( B^c \) for the complement of \( B \). The complement includes all elements that are in the universal set \( U \), but not in the subset \( B \).
In our exercise, the set \( B \) is defined as the even numbers within our universal set:
In our exercise, the set \( B \) is defined as the even numbers within our universal set:
- \( B = \{ 2, 4, 6, 8, 10 \} \)
- \( B^c = \{ 1, 3, 5, 7, 9, 11, 12 \} \)
Cardinality
Cardinality in set theory refers to the count of elements in a set. It gives a measure of the "size" of a set. For any given set \( S \), its cardinality is denoted as \( |S| \). In our exercise, we calculated the cardinality of the set complement \( B^c \).
- First, note that \( B^c = \{ 1, 3, 5, 7, 9, 11, 12 \} \).
- The cardinality of \( B^c \) is the number of elements in this complement set.
- By counting these elements, we determine that \( |B^c| = 7 \).
Natural Numbers
Natural numbers are the set of positive integers that begin from 1 and continue incrementally:
- \( \{ 1, 2, 3, 4, 5, \ldots \} \)