Chapter 1: Problem 5
Write out the addition and multiplication tables for \(\mathbb{Z}_{4}\)
Short Answer
Expert verified
Addition table: results modulo 4; Multiplication table: results modulo 4.
Step by step solution
01
Understanding \(\mathbb{Z}_{4}\)
\(\mathbb{Z}_{4}\) is the set of integers \(\{0, 1, 2, 3\}\) under addition and multiplication modulo 4. This means we'll add or multiply numbers and then take the remainder when divided by 4.
02
Constructing the Addition Table
Create a table where each element is the sum of the corresponding row and column entry modulo 4. For example, adding 2 and 3 in the system gives \(2 + 3 = 5\), but since we are using modulo 4, we take the remainder when dividing by 4: \(5 \mod 4 = 1\).
03
Addition Table for \(\mathbb{Z}_{4}\)
\(\begin{array}{c|cccc}+ & 0 & 1 & 2 & 3 \\hline0 & 0 & 1 & 2 & 3 \1 & 1 & 2 & 3 & 0 \2 & 2 & 3 & 0 & 1 \3 & 3 & 0 & 1 & 2 \\end{array}\)
04
Constructing the Multiplication Table
Create a table where each element is the product of the corresponding row and column entry modulo 4. For example, multiplying 2 and 3 gives \(2 \times 3 = 6\), and since we use modulo 4, we take the remainder when dividing by 4: \(6 \mod 4 = 2\).
05
Multiplication Table for \(\mathbb{Z}_{4}\)
\(\begin{array}{c|cccc}\times & 0 & 1 & 2 & 3 \\hline0 & 0 & 0 & 0 & 0 \1 & 0 & 1 & 2 & 3 \2 & 0 & 2 & 0 & 2 \3 & 0 & 3 & 2 & 1 \\end{array}\)
06
Review and Summary
In \(\mathbb{Z}_{4}\), addition and multiplication are performed with results taken modulo 4, ensuring all results stay within the set \(\{0, 1, 2, 3\}\). The constructed tables provide a closed system for these operations.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
addition modulo
When dealing with addition in modular arithmetic, think of it as a clock returning to its starting point. In the case of \( \mathbb{Z}_{4} \), the numbers involved are \( 0, 1, 2, \) and \( 3 \). This is similar to a clock with four numbers. Every time we perform an addition, we check if our sum needs to "wrap around" by keeping it within these numbers.
- For example, if we add \( 2 \) and \( 3 \), we actually get \( 5 \). However, since \( 5 \) is outside our set, we find how far \( 5 \) is from the nearest multiple of \( 4 \). Here, \( 5 \mod 4 \) returns \( 1 \), reflecting back into our circle of numbers.
- The addition table for \( \mathbb{Z}_{4} \) reminds us of this property. Adding numbers and finding their place within \( \mathbb{Z}_{4} \) uses this 'wrap around' concept, much like starting back at zero on a four-hour clock.
multiplication modulo
Multiplication modulo, similar to addition, requires us to control our results inside the set defined by the modulus. In \( \mathbb{Z}_{4} \), after multiplying two numbers, we take the remainder of the result when divided by \( 4 \).
- For instance, when multiplying \( 2 \) and \( 3 \), the product \( 6 \) exceeds our modulus limit. Therefore, we compute \( 6 \mod 4 \), resulting in \( 2 \). This means multiplying \( 2 \) by \( 3 \) in \( \mathbb{Z}_{4} \) stays located at \( 2 \) within our set.
- The multiplication table for \( \mathbb{Z}_{4} \) helps visualize this clearly as it aligns results within a repeated pattern that remains within \{0, 1, 2, 3\}. This systematic approach helps manage any calculations exceeding our set's numbers.
cyclic groups
A fascinating concept discovered through operations in \( \mathbb{Z}_{4} \) is the idea of cyclic groups. These are groups in mathematics where every element can be generated from one single element through repeated operations. In the context of \( \mathbb{Z}_{4} \), this means using operations like addition repeatedly.
- For instance, starting with \( 1 \) and successively adding itself (while respecting modular arithmetic rules), we can generate all other numbers in \( \mathbb{Z}_{4} \). This property characterizes \( \mathbb{Z}_{4} \) as a cyclic group because you can start from \( 1 \) and reach all elements like \( 0, 1, 2, \) and \( 3 \).
- Cyclic groups reveal the internal structure of sets like \( \mathbb{Z}_{4} \), showing how tightly connected the numbers are through repeated operations. This connection powers a variety of applications in computer science, cryptography, and coding theory.