Set Theory Proof: A∩B=Ø implies C∩D=Ø

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Homework Help Overview

The problem involves set theory, specifically examining the relationship between sets A, B, C, and D under the condition that A∩B=Ø and the implications for C∩D. The original poster seeks to understand whether the statement is a biconditional and how to approach proving it.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the nature of the statement, questioning whether it is indeed biconditional or simply an implication. There is an exploration of examples to clarify the relationships between the sets.

Discussion Status

Some participants have provided clarifications regarding the structure of the statement, noting that the original conjecture may be false. An example involving specific sets has been shared to illustrate the point, prompting further discussion and understanding.

Contextual Notes

There is a focus on the definitions of the sets and their relationships, with participants questioning the correctness of the subset relationships and the implications of the intersection being empty.

dainty77
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Homework Statement



Hey guys!

I am new to this forum but saw the helpful posts on set theory proofs and wondered if I could finally get some help with this problem:

Suppose A, B, C, and D are sets with A⊆C and B⊆D. If A∩B=Ø then C∩D=Ø.

This is a biconditional so I have to prove it both ways correct?

Any help would be greatly appreciated!


Homework Equations





The Attempt at a Solution

 
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dainty77 said:
Suppose A, B, C, and D are sets with A⊆C and B⊆D. If A∩B=Ø then C∩D=Ø.
Where's the biconditional? I only see an if then, not an if and only if. What work have you done?As stated, the conjecture is false. Are you sure you have the sense correct in terms of which sets are subsets of some other set?
 
My mistake, it is an "if then" statement.
 
As I previously said, the conjecture as written is false. For example, consider sets of fruits. Let A={apple}, B={banana}, C={apple, orange}, and D={banana, orange}. With this, A⊆C, B⊆D, and A∩B=Ø, but C∩D={orange}, which is not the null set.
 
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Wow, the example of using fruit really helped clarify it a lot more. Thank you so much!
 

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