Understanding Absorption Laws (Boolean Algebras)

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Discussion Overview

The discussion centers around the absorption laws in Boolean algebras, specifically how to derive the expression \( a \vee (a \land b) = a \). Participants are exploring the steps involved in this derivation, including the application of distribution law and the use of truth tables.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about obtaining the expression \( a \land (\top \vee b) \) and questions the application of the distribution law.
  • Another participant suggests that the absorption law can be derived by following specific logical steps, including the use of \( (a \land \top) \) and the distribution of \( \land \) over \( \vee \).
  • A later reply corrects a previous expression to \( a \land (\top \vee b) \) and emphasizes that this leads to \( a \) when \( \top \vee b \) is simplified to \( \top \).
  • One participant mentions the possibility of using a truth table to verify the equality of the two expressions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the derivation process, as there are differing views on the application of the distribution law and the steps required to arrive at the final expression.

Contextual Notes

Some participants reference specific logical steps and corrections but do not fully resolve the confusion regarding the application of the distribution law or the derivation of certain expressions.

mathrookie
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TL;DR
I cannot apply distribution law
I can't understand how absorption law is obtained. I get following steps.##a∨(a∧𝑏) = (a∧⊤)∨(a∧𝑏)##
##=(a∨a)∧(a∨b)∧(⊤∨a)∧(⊤∨b)##
then,

I come up with ##=a∧(a∨b)∧⊤∧⊤## so ##=a∧(a∨b)##

But, I cannot get ##a∧(⊤∨𝑏)##, as shown on here, therefore ##a##.

Can you help me? I cannot obtain ##a∧(⊤∨𝑏)## Some people say in other answers in different questions, it is obtained by distribution law. However, what I got by this is the first equation.
[1]: https://proofwiki.org/wiki/Absorption_Laws_(Boolean_Algebras)
 
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mathrookie said:
TL;DR Summary: I cannot apply distribution law

I can't understand how absorption law is obtained. I get following steps.##a∨(a∧𝑏) = (a∧⊤)∨(a∧𝑏)##
##=(a∨a)∧(a∨b)∧(⊤∨a)∧(⊤∨b)##
Your expression above doesn't help.
Follow the logic in your link to get this:
##a ∨ (a∧𝑏) = (a∧⊤)∨(a∧𝑏)##
##= a ∧ (T ∨ b) ## ∧ distributes over ∨
## = a ∧ T = a## T ∨ b = T
Edited to fix earlier typo.
mathrookie said:
then,

I come up with ##=a∧(a∨b)∧⊤∧⊤## so ##=a∧(a∨b)##

But, I cannot get
##a∧(⊤∨𝑏)##, as shown on here, therefore ##a##.

Can you help me? I cannot obtain
##a∧(⊤∨𝑏)## Some people say in other answers in different questions, it is obtained by distribution law. However, what I got by this is the first equation.
[1]: https://proofwiki.org/wiki/Absorption_Laws_(Boolean_Algebras)
 
Last edited:
Mark44 said:
Your expression above doesn't help.
Follow the logic in your link to get this:
##a ∨ (a∧𝑏) = (a∧⊤)∨(a∧𝑏)##
##= a ∧ (T ∧ b) ## ∧ distributes over ∨
## = a ∧ T = a## T ∨ b = T
Slight typo here, should be ##a\wedge(\top\vee b)##
OP, you can also use a truth table to see that the two expressions must be equal to a.
 
TeethWhitener said:
Slight typo here, should be ##a\wedge(\top\vee b)##
Right. I've fixed it in my post.
 
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