(A + B)·(Ā + C)·(B + C) — Boolean simplification

coreconsensus in POS; (B + C) is redundant

Answer

A′ · B + A · C

Why this example is worth doing

The dual of the consensus example, and the form in which the theorem is actually needed when you are working from a product of sums. (B + C) is the consensus of (A + B) and (Ā + C) and drops out. Students who have only memorised the SOP statement of consensus do not recognise it here, which is the point of carrying both. The page prints the minimal SOP too so you can see that the same function has a two-term sum and a two-factor product of the same cost.

Try your own input in the Boolean algebra simplifier. Simplify any expression to its minimal SOP and POS, one named law at a time.

How the answer is reached

Step by step

(A + B) · (A′ + C) · (B + C)A · (A′ + C) · (B + C) + B · (A′ + C) · (B + C)Distributive — A · (B + C) = A · B + A · C

A · (A′ + C) · (B + C) + B · (A′ + C) · (B + C)A · A′ · (B + C) + A · C · (B + C) + B · (A′ + C) · (B + C)Distributive — A · (B + C) = A · B + A · C

A · A′ · (B + C) + A · C · (B + C) + B · (A′ + C) · (B + C)0 · (B + C) + A · C · (B + C) + B · (A′ + C) · (B + C)Complement — A · A′ = 0

0 · (B + C) + A · C · (B + C) + B · (A′ + C) · (B + C)0 + A · C · (B + C) + B · (A′ + C) · (B + C)Null (annihilation) — A · 0 = 0

0 + A · C · (B + C) + B · (A′ + C) · (B + C)A · C · (B + C) + B · (A′ + C) · (B + C)Identity — A + 0 = A

A · C · (B + C) + B · (A′ + C) · (B + C)A · C · B + A · C · C + B · (A′ + C) · (B + C)Distributive — A · (B + C) = A · B + A · C

A · C · B + A · C · C + B · (A′ + C) · (B + C)A · C · B + A · C + B · (A′ + C) · (B + C)Idempotent — A · A = A

A · C · B + A · C + B · (A′ + C) · (B + C)A · C · B + A · C + B · A′ · (B + C) + B · C · (B + C)Distributive — A · (B + C) = A · B + A · C

A · C · B + A · C + B · A′ · (B + C) + B · C · (B + C)A · C · B + A · C + B · A′ · B + B · A′ · C + B · C · (B + C)Distributive — A · (B + C) = A · B + A · C

A · C · B + A · C + B · A′ · B + B · A′ · C + B · C · (B + C)A · C · B + A · C + B · A′ + B · A′ · C + B · C · (B + C)Idempotent — A · A = A

A · C · B + A · C + B · A′ + B · A′ · C + B · C · (B + C)A · C · B + A · C + B · A′ + B · A′ · C + B · C · B + B · C · CDistributive — A · (B + C) = A · B + A · C

A · C · B + A · C + B · A′ + B · A′ · C + B · C · B + B · C · CA · C · B + A · C + B · A′ + B · A′ · C + B · C + B · C · CIdempotent — A · A = A

A · C · B + A · C + B · A′ + B · A′ · C + B · C + B · C · CA · C · B + A · C + B · A′ + B · A′ · C + B · C + B · CIdempotent — A · A = A

A · C · B + A · C + B · A′ + B · A′ · C + B · C + B · CA · C · B + A · C + B · A′ + B · A′ · C + B · CIdempotent — A + A = A

A · C · B + A · C + B · A′ + B · A′ · C + B · CA · B · C + A · C + A′ · B + A′ · B · C + B · CCommutative — A · B = B · A; A + B = B + A

A · B · C + A · C + A′ · B + A′ · B · C + B · CA · C + A′ · B + A′ · B · C + B · CAbsorption — A + A · B = A

A · C + A′ · B + A′ · B · C + B · CA · C + A′ · B + B · CAbsorption — A + A · B = A

A · C + A′ · B + B · CA · C + A′ · BConsensus — A · B + A′ · C + B · C = A · B + A′ · C

Warning:

(A + B) · (A′ + C) · (B + C) simplifies to A · C + A′ · B in 18 steps. That is a proven minimum (2 terms, 4 literals), not a best effort. It is the only minimum-cost form.

Quine–McCluskey

Prime implicants — Quine–McCluskey
#Term
1A′ · B
2B · C
3A · C
Minimum cover — Quine–McCluskey
#Cover
1A′ · B + A · C
Warning:

2 term(s), 4 literal(s); 2 essential prime implicant(s).

Truth table

Truth table — columns #, A, B, C, F
#ABCF
00000
10010
20101
30111
41000
51011
61100
71111

Compare with

Open this example in the Boolean algebra simplifier

The field arrives filled in with this example’s input.

Note:

Notation this page assumes

  • Symbols: · is AND, + is OR, ⊕ is XOR, a prime or an overline is NOT. The field also takes ∧ ∨ ¬ ~ ! & | and the words.
  • Operator precedence, tightest first: NOT, then AND (including juxtaposition), then XOR/XNOR, then NAND/NOR, then OR, then IMPLIES, then IFF.
  • In a minterm index the first variable is the most significant bit, so over [A, B, C] minterm 5 is A·B̄·C.

Sources

  • Boole, An Investigation of the Laws of Thought (1854)
  • Shannon, “A Symbolic Analysis of Relay and Switching Circuits” (1938)