Boolean Algebra Proof (Distribution and XOR)

AI Thread Summary
The discussion revolves around proving the distributive rule of Boolean algebra involving exclusive or (XOR): A*(B XOR C) = (A*B) XOR (A*C). The user attempts various algebraic manipulations but initially struggles with applying DeMorgan's Rule correctly. After several iterations, they realize the importance of recognizing that terms like A*A' become zero, simplifying the proof. Ultimately, they successfully demonstrate the distributive property by correctly applying Boolean algebra principles. The conversation highlights the challenges of working with XOR and the necessity of understanding foundational rules in Boolean algebra.
PhotonSSBM
Homework Helper
Messages
154
Reaction score
59

Homework Statement


Use the definition of exclusive or (XOR), the facts that XOR commutes and
associates (if you need this) and all the non-XOR axioms and theorems you know
from Boolean algebra to prove this distributive rule:

A*(B (XOR) C) = (A*B) (XOR) (A*C)

Homework Equations


All the boolean algebra theorems

The Attempt at a Solution


So here's what I've tried

A*(B (XOR) C)
=A*B*C' + A*B'*C
=A*X+A*X'
=A*1
=A*(X (XOR) X')

And

(A*B) (XOR) (A*C)
=A*B*(A*C)' + (A*B)'*B*C
=A*B*(A' + C') + (A' + B')*B*C
=A*B*A' + A*B*C' + A'*B*C + B'*B*C
=A*B*C' + A'*B*C
=B*(A (XOR) C)
I feel like I go in circles no matter what I do.
Any clues?
 
Physics news on Phys.org
PhotonSSBM said:
=A*X+A*X'
This looks wrong. :))
PhotonSSBM said:
=A*B*(A*C)' + (A*B)'*B*C
Mistake here, too. :H
 
Oops, that's not how demorgans works...brb with corrections.
 
Ok, the answer came out once I realized how to use DeMorgan's Rule for the right hand side:

(A*B) (XOR) (A*C)
=(A*B) * (A*C)' + (A*B)' * (A*C)
=A*B * (A' + C') + (A' + B') * A*C
=A*A'*B + A*B*C' + A'*A*C + B'*A*C
=A*B*C' + A*B'*C
=A*(B*C' + B'*C)
=A* [B (XOR) C]

Thanks for the help!
 
Last edited:
in the next step:
=A*A'*B + A*B*C' + A'*A*C + B'*A*C
=A*B*C' + A*B'*C

what happened with (A*A'*B + A'*A*C)?
 
Hi,

Raimundo said:
what happened with (A*A'*B + A'*A*C)?

I think those go to zero as ## A \cdot \bar A = 0 ##
 
Back
Top