Why is the Absorption Law of Propositional Logic so ?
p $\lor (p \land q) \equiv$ p
Would appreciate an intuitive explanation and not one using a Truth Table
Why is the Absorption Law of Propositional Logic so ?
p $\lor (p \land q) \equiv$ p
Would appreciate an intuitive explanation and not one using a Truth Table
On
When we have an or statement either the left hand side or the right needs to be true for it to be true. In this case we have p on the left and $ (p \land q)$ on the right. But $ (p \land q)$ can only be true if p and q are both true. But if p is true we can immediately deduce that the or statement is true without knowing the value of q (since the LHS will be true). We can also immediately tell that if p were false then both the left and right would be false; therefore, the statement is false. So basically all the absorbtion law is saying is that the truth vaule of this or statement is only dependent on p, we do not need q to determine whether it is true or not.
On
As you can see in this link (Prove the absorption law in propositional logic)
p ∨ (p ∧ q) ≡ p ∧ (p ∨ q) ≡ p
explained by derivation with Morgan's Laws
T stands for True
p ≡ (p ∧ T) (by inverting null element)
so
p ∨ (p ∧ q) ≡ (p ∧ T) ∨ (p ∧ q)
(p ∧ T) ∨ (p ∧ q) ≡ p ∧ (T ∨ q) (by inverting distribution law)
(T ∨ q) ≡ T (by absorbent element)
so
p ∧ (T ∨ q) ≡ p ∧ T
p ∧ T ≡ p (by null element)
From a Venn Diagram standpoint, all of $A$ plus any subset of $A$ will still just be $A$