Boolean algebraic theorems are a set of proven rules used to simplify Boolean expressions without changing their output. These theorems define how the Boolean operators AND (·), OR (+), and NOT (') work with the binary values 0 and 1, making logic expressions easier to understand and digital circuits simpler to design.
Example: In the expression, A + 0 = A
Solution:
Using the Identity Theorem:
If A = 0:
LHS = 0 + 0 = 0 = RHSIf A = 1:
LHS = 1 + 0 = 1 = RHSHence, A + 0 = A is proved.
Question 1: Using De Morgan's Theorem, simplify the Boolean expression: F = (A + B)'.
Solution:
Given, F = (A + B)'
Using De Morgan's Theorem,
(A + B)' = A'B'
Therefore,
F = A'B'
Question 2: Find the dual of the Boolean expression: F = A + 0.
Solution:
Given, F = A + 0
Using the Duality Theorem, replace every:
+with.0with1Therefore, F = A . 1
Question 3: Simplify the Boolean expression: F = (A')'
Solution:
Given, F = (A')'
Using the Inversion Law,
(A')' = A
Therefore, F = A
Question 4: Using the Commutative and Associative Laws, rewrite the Boolean expression so that similar terms are grouped together. F = C + A + B + A.C
Solution:
Given, F = C + A + B + AC
Using the Commutative Law, rearrange the terms.
F = A + AC + B + C
Now the related terms are grouped together.
Using the Redundancy Theorem,
A + AC = A
Therefore, F = A + B + C.
Question 5: Using Boolean theorems, prove that the following expression is always equal to 1. F = (A + B)(A' + B')
Solution:
Given, F = (A + B)(A' + B')
Apply the Distributive Law.
F = AA' + AB' + BA' + BB'
Using the Complementary Theorem,
AA' = 0
BB' = 0
Therefore, F = AB' + A'B.
Question 6: Which Boolean theorem is most appropriate for simplifying each of the following expressions?
- (A + B)'
- (A')'
- A + AB
- A(B + C)
Solution:
- (A + B)' → De Morgan's Theorem
- (A')' → Inversion Law
- A + AB → Redundancy (Absorption) Theorem
- A(B + C) → Distributive Law.
Practice Questions
Question 1: Simplify the Boolean expression using De Morgan's Theorem: F = (AB)'
Question 2: Find the dual of the Boolean expression: F = A . 0
Question 3: Using the Distributive Law, expand the Boolean expression: F = A(B + C + D)
Question 4: Verify whether the following expression satisfies the Complementary Theorem: F = A + A'
Question 5: Rewrite the following Boolean expression using the Commutative and Associative Laws: F = C.A + B + A + C