Question
Among the statements (S1) : is a tautology (S2) : is a contradiction
Options
Solution
Key Concepts and Formulas
- Implication (): This is false only when is true and is false. Otherwise, it is true.
- Negation (): This is true when is false, and false when is true.
- Conjunction (): This is true only when both and are true.
- Disjunction (): This is true when either or or both are true. It is false only when both and are false.
- Tautology: A statement that is always true, regardless of the truth values of its components.
- Contradiction: A statement that is always false, regardless of the truth values of its components.
Step-by-Step Solution
Step 1: Analyze Statement S1:
We need to determine if the given statement is a tautology. We'll construct a truth table to evaluate the statement for all possible truth values of and .
Step 2: Construct the Truth Table for S1
- Column 1 & 2 (p & q): All possible combinations of truth values for and .
- Column 3 (): Negation of . If is true, is false, and vice versa.
- Column 4 (): Conjunction of and . It is true only when both and are true.
- Column 5 (): Implication of to . It is false only when is true and is false.
- Column 6 (): Disjunction of and . It is true if either or or both are true.
Step 3: Determine if S1 is a Tautology
From the last column of the truth table, we see that the statement is not always true. It is false when is true and is false. Therefore, S1 is not a tautology.
Step 4: Analyze Statement S2:
We need to determine if the given statement is a contradiction. We'll construct a truth table to evaluate the statement for all possible truth values of and .
Step 5: Construct the Truth Table for S2
- Column 1 & 2 (p & q): All possible combinations of truth values for and .
- Column 3 (): Negation of . If is true, is false, and vice versa.
- Column 4 (): Implication of to . It is false only when is true and is false.
- Column 5 : Conjunction of and . It is true only when both and are true.
- Column 6 : Implication of to . It is false only when is true and is false.
Step 6: Determine if S2 is a Contradiction
From the last column of the truth table, we see that the statement is not always false. It is true when is false and is true. Therefore, S2 is not a contradiction.
Common Mistakes & Tips
- Be careful with the truth table for implication. is only false when is true and is false.
- Remember the definitions of tautology and contradiction.
- It is very helpful to create a truth table for each statement separately.
Summary
We analyzed the two statements S1 and S2 using truth tables. We found that S1 is not a tautology because it is false when is true and is false. We also found that S2 is not a contradiction because it is true when is false and is true. Therefore, neither S1 nor S2 is true.
Final Answer
The final answer is \boxed{neither (S1) and (S2) is True}, which corresponds to option (A).