Consider the statements: I. A ⇔ A ∨ ~ A II. A ⇔ A ∨ A III. A ∨ B ⇒ A IV. A ⇒ A ∨ B Which of the above refers to tautologies?
Consider the statements: I. A ⇔ A ∨ ~ A II. A ⇔ A ∨ A III. A ∨ B ⇒ A IV. A ⇒ A ∨ B Which of the above refers to tautologies? Correct Answer II and IV
The correct answer is option 4.
Concept:
Tautology:
A tautology is a compound statement in Maths that always results in Truth value.
I. A ⇔ A ∨ ~ A:
False, not a tautology.
| A | ~ A | A ∨ ~ A | A ⇔ A ∨ ~ A |
| True | False | True | True |
| False | True | True | False |
II. A ⇔ A ∨ A
True, The compound statement is a tautology.
| A | A ∨ A | A ⇔ A ∨ A |
| True | True | True |
| False | False | True |
III. A ∨ B ⇒ A
False, not a tautology.
| A | B | A ∨ B | A ∨ B ⇒ A |
| True | True | True | True |
| True | False | True | True |
| False | True | True | False |
| False | False | False | True |
IV. A ⇒ A ∨ B
True, The compound statement is a tautology.
| A | B | A ∨ B | A ⇒ A ∨ B |
| True | True | True | True |
| True | False | True | True |
| False | True | True | True |
| False | False | False | True |
Hence the correct answer is II and IV.
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Feb 20, 2025