Page 15 - Chapter 2

• Logically Equivalent

If two statements p and q are always either both true

or both false, for any values of the propositional

variables, namely

p  q is a tautology

Then we call p and q are logically equivalent.

Denoted by

p ≡ q

• Example 6

Show that p V q and q V p are logically equivalent

The truth table of (p V q )  (q V p ) are shown as follows

Truth Table :

p q p V q q V p p V q q V p

T T T T T

T F T T T

F T T T T

F F F F T