Νόμοι De Morgan
- Ένα Θεώρημα των Μαθηματικών.
Ετυμολογία[]
Πρότυπο:Theorems
Η ονομασία "Θεώρημα" σχετίζεται ετυμολογικά με το όνομα του μαθηματικού "[[]]".
Περιγραφή[]
In propositional logic and boolean algebra, De Morgan's laws[1][2][3] are a pair of transformation rules that are both valid rules of inference. They are named after Augustus De Morgan, a 19th-century British mathematician. The rules allow the expression of conjunctions and disjunctions purely in terms of each other via negation.
The rules can be expressed in English as:
- the negation of a disjunction is the conjunction of the negations; and
- the negation of a conjunction is the disjunction of the negations;
or
- the complement of the union of two sets is the same as the intersection of their complements; and
- the complement of the intersection of two sets is the same as the union of their complements.
or
- not (A or B) = not A and not B; and
- not (A and B) = not A or not B
In set theory and Boolean algebra, these are written formally as
where
- A and B are sets,
- Πρότυπο:Overline is the complement of A,
- ∩ is the intersection, and
- ∪ is the union.
In formal language, the rules are written as
and
where
- P and Q are propositions,
- is the negation logic operator (NOT),
- is the conjunction logic operator (AND),
- is the disjunction logic operator (OR),
- is a metalogical symbol meaning "can be replaced in a logical proof with".
Applications of the rules include simplification of logical expressions in computer programs and digital circuit designs. De Morgan's laws are an example of a more general concept of mathematical duality.
Formal notation[]
The negation of conjunction rule may be written in sequent notation:
The negation of disjunction rule may be written as:
In rule form: negation of conjunction
and negation of disjunction
and expressed as a truth-functional tautology or theorem of propositional logic:
where and are propositions expressed in some formal system.
Substitution form[]
De Morgan's laws are normally shown in the compact form above, with negation of the output on the left and negation of the inputs on the right. A clearer form for substitution can be stated as:
This emphasizes the need to invert both the inputs and the output, as well as change the operator, when doing a substitution.
Set theory and Boolean algebra[]
In set theory and Boolean algebra, it is often stated as "union and intersection interchange under complementation",[4] which can be formally expressed as:
where:
- Πρότυπο:Overline is the negation of A, the overline being written above the terms to be negated,
- ∩ is the intersection operator (AND),
- ∪ is the union operator (OR).
The generalized form is:
where I is some, possibly uncountable, indexing set.
In set notation, De Morgan's laws can be remembered using the mnemonic "break the line, change the sign".[5]
Υποσημειώσεις[]
- ↑ Copi and CohenΠρότυπο:Full citation needed
- ↑ Hurley, Patrick J. (2015), A Concise Introduction to Logic (12th έκδοση), Cengage Learning, ISBN 978-1-285-19654-1
- ↑ Moore and ParkerΠρότυπο:Full citation needed
- ↑ Boolean Algebra by R. L. Goodstein.
- ↑ 2000 Solved Problems in Digital Electronics by S. P. Bali
Εσωτερική Αρθρογραφία[]
- Μαθηματικά
- Άλγεβρα
- Γεωμετρία
- Μαθηματική Ανάλυση
- Τοπολογία
- Μαθηματική Αρχή
- Μαθηματικό Θεώρημα
- Μαθηματικά Θεωρήματα
- Μαθηματικό Αξίωμα
- Μαθηματικός Χώρος
Βιβλιογραφία[]
Ιστογραφία[]
Κίνδυνοι Χρήσης |
---|
Αν και θα βρείτε εξακριβωμένες πληροφορίες "Οι πληροφορίες αυτές μπορεί πρόσφατα Πρέπει να λάβετε υπ' όψη ότι Επίσης, |
- Μην κάνετε χρήση του περιεχομένου της παρούσας εγκυκλοπαίδειας
αν διαφωνείτε με όσα αναγράφονται σε αυτήν
- Όχι, στις διαφημίσεις που περιέχουν απαράδεκτο περιεχόμενο (άσεμνες εικόνες, ροζ αγγελίες κλπ.)