Proving Powerset P and Intersection N: A Midterm Study Guide

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Discussion Overview

The discussion revolves around proving the relationship between the powerset of the intersection of two sets and the intersection of their powersets, specifically the claim that P(A ∩ B) = P(A) ∩ P(B). The context is a study guide for a midterm exam, focusing on set theory concepts.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant requests help with proving that P(A ∩ B) = P(A) ∩ P(B), expressing confusion about the proof process.
  • Another participant suggests that the proof can be done by applying definitions and outlines a method to show that if x is in P(A ∩ B), then x is also in P(A) ∩ P(B), and vice versa.
  • A different participant expresses uncertainty about which definitions to use, noting that their textbook lacks detailed information on powersets beyond the basic definition.
  • One participant provides a detailed explanation of the proof, stating that if x is in P(A ∩ B), then x must be a subset of A ∩ B, leading to the conclusion that x is in both P(A) and P(B).
  • There is a clarification regarding the terminology, with one participant correcting another about the correct phrasing of elements and subsets in the context of powersets.
  • A participant mentions their unfamiliarity with set theory, indicating that it was removed from their curriculum and is not commonly used in their undergraduate physics courses.

Areas of Agreement / Disagreement

Participants generally agree on the approach to proving the statement using definitions, but there is some confusion regarding terminology and the depth of understanding of set theory concepts. No consensus is reached on the clarity of the textbook or the definitions needed for the proof.

Contextual Notes

Some participants express uncertainty about the definitions and concepts related to powersets and set theory, indicating a potential gap in foundational knowledge that may affect their ability to engage with the proof effectively.

Who May Find This Useful

Students studying set theory, particularly those preparing for exams or seeking clarification on powersets and intersections in mathematical contexts.

Klion
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P for powerset, n for intersection

show that P(AnB)=P(A) n P(B)

Studying for a midterm, seen this question in our textbook and on an old midterm. No idea how to do it. Anyone know?
 
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It's pretty basic, just apply definitions, and you should be ok.
Just prove that if x is in P(A ∩ B) then x is also in P(A) ∩ P(B), and
that if x is in P(A) ∩ P(B) then x is in P(A ∩ B).

It should just be applying definitions.
 
I know the idea behind doing a proof heh, I think my textbook is somewhat lacking though. What definitions shoudl I be attempting to make use of. Only info I've found on powersets in textbook is what the powerset actually is (the set containing all the subsets). Cant think of any helpful way to apply that to a general case though.
 
Ok:

x is in P(A ∩ B) is equivalent to saying that
x is a subset of A ∩ B
so each element χ of x is in A ∩ B
so each element χ of x is in A and in B
so x is a subset of A and x is a subset of B
so x is in P(A) and x is in P(B)

you should have no problem filling in the holes, and going in the other direction from there.
 
Shouldn't that be x is an element of...
 
Shouldn't that be x is an element of...

No, x is a subset of A∩B is correct.

x is an element of P(A∩B) which is the collection of all subsets of A∩B.
 
I see, set theory is quite new to me, it was taken off our curriclum at school and isn't much used in undergraduate physics (well not in the first year anyway).
 

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