Having some issue with some logic - the examples I've been provided with arn't very helpful so I can have no idea where to start. The question is to prove;
(p ∨ q) ∧ (q ⇒ p) ≡ p
but I have no idea where to start. Attached below are the rules I'm using.
A ∧ A ≡ A, A ∨ A ≡ A idempotence
A ∧ B ≡ B ∧ A, A ∨ B ≡ B ∨ A commutativity
A ∧ (B ∧ C ) ≡ (A ∧ B) ∧ C , A ∨ (B ∨ C ) ≡ (A ∨ B) ∨ C associativity
A ∧ (A ∨ B) ≡ A, A ∨ (A ∧ B) ≡ A absorption
A ∧ (B ∨ C ) ≡ (A ∧ B) ∨ (A ∧ C ) distributivity
A ∨ (B ∧ C ) ≡ (A ∨ B) ∧ (A ∨ C ) distributivity
A ∧ (¬A) ≡ false, A ∨ (¬A) ≡ true negation
¬(¬A) ≡ A double negation
¬(A ∧ B) ≡ (¬A) ∨ (¬B), ¬(A ∨ B) ≡ (¬A) ∧ (¬B) de Morgan
A ⇒ B ≡ (¬A) ∨ B implication
A ⇔ B ≡ (A ⇒ B) ∧ (B ⇒ A) bi-implication
My first guess is to use the rule of implication first but to be honest, I have no idea where to start.
Would really appreciate any help anyone can provide.
Thanks.
Another solution:
$(p \lor q) \land(q \rightarrow p)$
$(p \lor q) \land(\neg q \lor p)$, implication
$(p \lor q) \land (p \lor \neg q)$, commutativity
$p \lor (q \land \neg q)$, distributivity
$p \lor \text{false}$, negation
$p \lor (p \land \neg p)$, negation again
$p$, absorption