Math Problem Statement
The degree sequence of a graph is the sequence of the degrees of the vertices of the graph in nonincreasing simple graph G is 4, 3, 3,2,2. a) Draw such a graph G. b) What is the degree sequence of complement of G? [3 Marks] p Marks] Prove or disprove that the given statement is a tautology using truth table. [5 Marks]
Solution
Let's break down the problem step by step.
Part (a): Draw a graph with degree sequence
Steps to construct the graph:
- We have 5 vertices labeled, say .
- The degree sequence means that vertex has degree 4, and have degree 3, and and have degree 2.
- Since vertex has degree 4, it must be connected to all other vertices.
- Now connect and to ensure they have degree 3, but ensure that and maintain degree 2 by carefully adding edges.
Here’s one possible graph:
- connects to (giving degree 4).
- connects to and (now has degree 3).
- connects to (now has degree 3, and both and have degree 2).
Part (b): Degree sequence of the complement of
In the complement of a graph, two vertices are adjacent if and only if they were not adjacent in the original graph.
- In the original graph, had degree 4, meaning it was connected to 4 vertices. In the complement graph, will be connected to 0 vertices (since it was connected to everyone).
- Vertices and had degree 3 in the original graph, so in the complement, each will be connected to 1 vertex.
- Vertices and had degree 2 in the original graph, so in the complement, each will be connected to 3 vertices.
Thus, the degree sequence of the complement graph is:
Part (c): Prove or disprove that the given statement is a tautology using a truth table
A tautology is a statement that is always true regardless of the truth values of the components.
Let the given statement be . Without the explicit statement provided, let's assume it's a logical formula involving variables , and so on. I will guide you through the steps to test it using a truth table.
- Identify the logical operators (e.g., AND, OR, NOT, implications).
- Create a truth table for all possible truth values of the involved variables.
- Evaluate the statement for each combination of truth values.
- Check if the final column is all TRUE—if it is, the statement is a tautology; otherwise, it is not.
If you provide the exact statement, I can construct the truth table and proceed with the proof.
Would you like further details or assistance on any of these steps?
Relative Questions:
- Can you describe how the degree sequence helps construct a graph?
- What are the properties of the complement of a graph?
- How would the degree sequence of a graph change if a vertex were removed?
- Why are truth tables important in proving logical statements?
- How does the degree of vertices affect the structure of a graph?
Tip:
When constructing graphs from a degree sequence, ensure that each step of adding edges keeps the overall degree sequence intact for all vertices involved.
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Math Problem Analysis
Mathematical Concepts
Graph Theory
Graph Complements
Logic
Truth Tables
Formulas
Degree Sequence of a Graph
Degree of Complement Graph
Theorems
Complement Graph Theorem
Tautology Definition
Suitable Grade Level
Grades 11-12