File talk:Propositional logic.png

Material Equivalence
There is an error on material equivalence, both conditions are necessary to make p equivalent to q: external link
 * image: (p is equiv. to q) means, either (if p is true then q is true) or (if q is true then p is true)
 * $$ (p \equiv q) \equiv [(p \rightarrow q) \lor (q \rightarrow p)]$$
 * correct: (p is equiv. to q) means, (if p is true then q is true) and (if q is true then p is true)
 * $$ (p \equiv q) \equiv [(p \rightarrow q) \land (q \rightarrow p)]$$