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==Proof==
 
==Proof==
 
Let x ∈ ''S'', where ''S'' is the universal set.
 
  
 
First we show that A ∩ Ø ⊂ Ø. <br/>
 
First we show that A ∩ Ø ⊂ Ø. <br/>
We know this is true because the set resulting from the union of two sets is a subset of both of the sets ([[Union_and_intersection_subsets_mh|proof]]).
+
We know this is true because the set resulting from the intersection of two sets is a subset of both of the sets forming the intersection ([[Union_and_intersection_subsets_mh|proof]]).
  
 
Next, we want to show that Ø ⊂ A ∩ Ø.<br/>
 
Next, we want to show that Ø ⊂ A ∩ Ø.<br/>
Let x ∈ Ø. The antecedent (i.e. the "if") part is false by definition of the empty set. Then x ∈ Ø ⇒ x ∈ (A ∩ Ø) is true and we have that Ø ⊂ A ∩ Ø.  
+
We know this is true because the empty set is a subset of all sets ([[empty_set_contained_in_every_set|proof]]).
  
 
Since A ∩ Ø ⊂ Ø and Ø ⊂ A ∩ Ø, we have that A ∩ Ø = Ø. <br/>
 
Since A ∩ Ø ⊂ Ø and Ø ⊂ A ∩ Ø, we have that A ∩ Ø = Ø. <br/>
 
<math>\blacksquare</math>
 
<math>\blacksquare</math>
 
 
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== References ==
 
 
* B. Ikenaga, [http://www.millersville.edu/~bikenaga/math-proof/setalg/setalg.pdf "Set Algebra and Proofs Involving Sets"] March 1st, 2008, [October 1st, 2013]
 
  
  
 
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[[Proofs_mhossain|Back to list of all proofs]]
 
[[Proofs_mhossain|Back to list of all proofs]]

Latest revision as of 05:11, 6 October 2013


Theorem

Let $ A $ be a set in S. Then
A ∩ Ø = Ø



Proof

First we show that A ∩ Ø ⊂ Ø.
We know this is true because the set resulting from the intersection of two sets is a subset of both of the sets forming the intersection (proof).

Next, we want to show that Ø ⊂ A ∩ Ø.
We know this is true because the empty set is a subset of all sets (proof).

Since A ∩ Ø ⊂ Ø and Ø ⊂ A ∩ Ø, we have that A ∩ Ø = Ø.
$ \blacksquare $



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Correspondence Chess Grandmaster and Purdue Alumni

Prof. Dan Fleetwood