• Support PF! Buy your school textbooks, materials and every day products Here!

Sets and De Morgan

  • Thread starter Krovski
  • Start date
  • #1
11
0

Homework Statement



I'm using Introduction to Analysis 5th edition by Edward D. Gaughan.

The question is:
Prove (De Morgan)
S\([itex]\bigcap[/itex] A[itex]_{\lambda}[/itex]) = [itex]\cup[/itex](S\A)
[itex]\lambda\epsilon[/itex] [itex]\Lambda[/itex]
Where [itex]\Lambda[/itex] A and S are sets
(doesn't specify real or complex but assuming real)


Homework Equations


to prove two things equal it is enough to show they are contained within each other
union is all elements of both sets, none repeat (ie if two appears twice count it only once)
intersection is all elements common to both sets

The Attempt at a Solution



(for typing purposes I'll just write everything out in words rather than symbols, having trouble from my tablet)
I can understand that if there is some x that belongs to this set, it is clear that it belongs to S and not the intersection of A[itex]\lambda[/itex]
On the right hand side of the equation I can see that if x is not in the intersection of A[itex]\lambda[/itex] and it is in S, then the union of the two sets would mean that x is in the right hand side of the equation since it's in S.

I don't think it is enough for what my Prof. is looking for. Any thoughts?
 

Answers and Replies

  • #2
96
0
Krovski, perhaps we can start off a little smaller.

Let A,B, and C be sets.

For three sets, the DeMorgan's Law in question states:

A-(B ∩ C) = (A - B) ∪ (A - C).

*I am using A-B to denote {x| x is in A and x is not in B}

Prove that first. Then, perhaps solving this will give us a better intuition for arbitrary unions and intersections.
 

Related Threads on Sets and De Morgan

Replies
3
Views
12K
  • Last Post
Replies
12
Views
6K
Replies
24
Views
3K
  • Last Post
Replies
13
Views
943
  • Last Post
Replies
0
Views
4K
Replies
1
Views
2K
Replies
1
Views
7K
Replies
1
Views
4K
Replies
14
Views
59K
Top