2/n-variable theorems

Covering theorem : a+aX = a , since a already covers the following minterm
Distributivity: x=yz = (x+y)(x+z)
Consensus Theorem : ab+a'c+bc = ab+a'c

Priniciple of Duality : Any theorem or identity remains true if 0 and
1 are swapped and . and + are swapped throughout.