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Gianfranco (talk | contribs) (Created page with "===<!--70-->Set operators=== <!--71-->Given the whole universe <math>U</math> <!--72-->we indicate with <math>x</math> <!--73-->its generic element so that <math>x \in U</math>; <!--74-->then, we consider two subsets <math>A</math> and <math>B</math> <!--75-->internal to <math>U</math> <!--76-->so that <math>A \subset U</math> <!--77-->and <math>B \subset U</math> {| |left|80px |'''<!--78-->Union:''' <!--79-->represented by the symbol <math>\cup</m...") |
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=== | ===Set operators=== | ||
Given the whole universe <math>U</math> we indicate with <math>x</math> its generic element so that <math>x \in U</math>; then, we consider two subsets <math>A</math> and <math>B</math> internal to <math>U</math> so that <math>A \subset U</math> and <math>B \subset U</math> | |||
{| | {| | ||
|[[File:Venn0111.svg|left|80px]] | |[[File:Venn0111.svg|left|80px]] | ||
|''' | |'''Union:''' represented by the symbol <math>\cup</math>, indicates the union of the two sets <math>A</math> and <math>B</math> <math>(A\cup B)</math>. It is defined by all the elements that belong to <math>A</math> and <math>B</math> or both: | ||
<math>(A\cup B)=\{\forall x\in U \mid x\in A \land x\in B\}</math> | <math>(A\cup B)=\{\forall x\in U \mid x\in A \land x\in B\}</math> | ||
|- | |- | ||
|[[File:Venn0001.svg|sinistra|80px]] | |[[File:Venn0001.svg|sinistra|80px]] | ||
|''' | |'''Intersection:''' represented by the symbol <math>\cap</math>, indicates the elements belonging to both sets: | ||
<math>(A\cap B)=\{\forall x\in U \mid x\in A \lor x\in B\}</math> | <math>(A\cap B)=\{\forall x\in U \mid x\in A \lor x\in B\}</math> | ||
|- | |- | ||
|[[File:Venn0010.svg|left|80px]] | |[[File:Venn0010.svg|left|80px]] | ||
|''' | |'''Difference:''' represented by the symbol <math>-</math>, for example <math>A-B</math> shows all elements of <math>A</math> except those shared with <math>B</math> | ||
|- | |- | ||
|[[File:Venn1000.svg|left|80px]] | |[[File:Venn1000.svg|left|80px]] | ||
|''' | |'''Complementary:''' represented by a bar above the name of the collection, it indicates by <math>\bar{A}</math> the complementary of <math>A</math>, that is, the set of elements that belong to the whole universe except those of <math>A</math>, in formulas: <math>\bar{A}=U-A</math><br /> | ||
|} | |} | ||
The theory of fuzzy language logic is an extension of the classical theory of sets in which, however, the principles of non-contradiction and the excluded third are not valid. Remember that in classical logic, given the set <math>A</math> and its complementary <math>\bar{A}</math>, the principle of non-contradiction states that if an element belongs to the whole <math>A</math> it cannot at the same time also belong to its complementary <math>\bar{A}</math>; according to the principle of the excluded third, however, the union of a whole <math>A</math> and its complementary <math>\bar{A}</math> constitutes the complete universe <math>U</math>. | |||
In other words, if any element does not belong to the whole, it must necessarily belong to its complementary. |
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