Understanding the Cardinality of Specific Sets

Understanding the Cardinality of Specific Sets

In this article, we will explore the concept of cardinality and understand the cardinality of two specific sets:
1. The set of all real numbers (x) such that (x^2 2).
2. The set of all integers (x) such that (x^2 2).

Set 1: Real Numbers

Let's first consider the set {x | x is a real number and (x^2 2)}. This set can be described as all real numbers (x) that satisfy the equation (x^2 2). Solving the equation (x^2 2), we find two real solutions: (x sqrt{2}) and (x -sqrt{2}). Thus, the set can be expressed as ({sqrt{2}, -sqrt{2}}). The cardinality of this set is 2, as it contains exactly two elements. Formally, this set can also be written as ({x in mathbb{R} | x^2 2}). This set has two elements, which we have shown as ({sqrt{2}, -sqrt{2}}).

Set 2: Integers

Next, let's look at the set {x | x is an integer and (x^2 2)}. This set consists of all integers (x) that satisfy the equation (x^2 2). However, there is no integer that, when squared, equals 2. The square root of 2 is approximately 1.414, which is not an integer. Therefore, this set is empty and can be written as (emptyset). The cardinality of this set is 0, as it contains no elements. Formally, this set can be written as ({x in mathbb{Z} | x^2 2}), which is the empty set (emptyset).

Cardinality of the Sets

In summary, the cardinality of the two sets is as follows: Cardinality of the set of real numbers (x) such that (x^2 2): 2 Cardinality of the set of integers (x) such that (x^2 2): 0

What is Cardinality?

Cardinality in mathematics refers to the number of elements in a set. It is a fundamental concept in set theory and has applications in various areas of mathematics, including computing and data analysis.

For the set of real numbers (x) where (x^2 2), the solutions are (x sqrt{2}) and (x -sqrt{2}). Thus, the set contains two elements, and its cardinality is 2.

For the set of integers (x) where (x^2 2), since there are no integer solutions, the set is empty, and its cardinality is 0.

Additional Insights

Let's delve into a few more insights and examples related to cardinality and the sets discussed earlier: The set ({x in mathbb{R} | x^2 For the set ({x in mathbb{R} | x^2 2}), we can write it as ({x in mathbb{R} | sqrt{x^2} sqrt{2}}), which simplifies to ({x in mathbb{R} | x pm sqrt{2}}). Similarly, for the set ({x in mathbb{Z} | x^2 2}), we note that (sqrt{2}) is not an integer, so the set is empty: ({x in mathbb{Z} | x pm sqrt{2}}) is (emptyset).

Conclusion

In conclusion, understanding the cardinality of sets is crucial in various mathematical and computational contexts. The sets we have discussed demonstrate how different sets can have varying cardinalities, with the set of real numbers (x) such that (x^2 2) having a cardinality of 2 and the set of integers (x) such that (x^2 2) being empty, thus having a cardinality of 0.

References

1. Ahlquist, N. (2020). Understanding Set Theory and Cardinality. [Online] Available at: 2. Li, C. Wang, F. (2023). Advanced Topics in Set Theory. [Online] Available at: