Laws (Theorems) of Boolean algebra Laws of Complementation oThe term complement means, to invert or to change 1's to 0's and 0's to 1's, for which purpose inverters or NOT gates are used. oA complement of a variable is represented by a bar over the letter. For example, the complement of a variable A will be denoted by | Website for Students | VTU NOTES | QUESTION PAPERS1
Law 1: = 1 Law 2: = 0 Law 3: If A = 0, Law 4: If A = 1, Law 5: | Website for Students | VTU NOTES | QUESTION PAPERS2
AND Laws Law 6: A.0=0 Law 7: A.1=A Law 8: A.A=A Law 9: | Website for Students | VTU NOTES | QUESTION PAPERS3
OR Laws Law 10: A +0 = A Law 11: A +1 = 1 Law 12: A +A = A Law 13: | Website for Students | VTU NOTES | QUESTION PAPERS4
Commutative Laws –This states that the order in which the variables are OR’ed and AND’ed will make no difference in the output. Law14: A. B = B. A Law 15 : A + B = B + A | Website for Students | VTU NOTES | QUESTION PAPERS5
Associative Laws This law states that the order in which the variables are grouped will not make any difference in the output. Law 16: A + (B + C) = (A + B) + C | Website for Students | VTU NOTES | QUESTION PAPERS6
Law 17: A.(B.C) = (A.B).C | Website for Students | VTU NOTES | QUESTION PAPERS7
Distributive Laws These laws allow the factoring or multiplying out of expressions. Law 18: A.(B +C) = (A.B) + (A.C) Law 19: A + (B.C) = (A + B) (A + C) | Website for Students | VTU NOTES | QUESTION PAPERS8
De Morgan's Theorems The complement of any Boolean expression is found by using these two rules. | Website for Students | VTU NOTES | QUESTION PAPERS9
Steps for complementation: 1. Replace ‘+’ symbols with ‘.’ symbols and ‘.’ symbols with ‘+’ symbols. 2. Complement each term. | Website for Students | VTU NOTES | QUESTION PAPERS10
Proof of De Morgan's Theorems | Website for Students | VTU NOTES | QUESTION PAPERS11
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