The Duality Principle (1.3)

The dual of an expression is obtained by exchanging (• and +), and (1 and 0) in it.

·         If a particular Boolean equation is valid, its dual is also valid.

·         One can replace   • by +  and   + by • and 0 by 1 and  1 by 0  in an equality and the resulting

equality remains true.

• The precedence of the operands must remain the same.
• Cannot exchange x with x’

Example: the expression c=(x+y)(y+z)’+xy is given.  By replacing the operations OR by the operation AND and vice-verse, the operations AND by the operation OR , the expression c_dual=(xy+(yz)’)(x+y) will be obtained.