DeMorgans laws and rules of logic

In summary, the negation of the conditional (p -> q) is equivalent to the statement, "I go to McDonalds and I don't get a Big Mac."
  • #1
jj0424
3
0

Homework Statement


(p -> q) has an unambiguous meaning both in logic and in natural language. The DeMorgans laws tell us what is meant by the negation of a conjunction or the negation of a disjunction, but what is the negation of a conditional such as p -> q? Use the rules of logic to produce a meaning for...[not(p -> q), and translate it into natural language using the statement, "If I go to McDonalds, then i will get a Big Mac."


Homework Equations



¬ ( p ˅ q ) <=> ( ¬p ˄ ¬ q )
¬ ( p ˄ q ) <=> ( ¬p ˅ ¬ q ) De Morgans laws

The Attempt at a Solution



( p  q ) => ( ¬ p ˅ q ) Implication
¬ ( p  q ) => ¬ ( ¬ p ˅ q ) Implication
¬ ( ¬ p ˅ q ) <=> ( p ˄ ¬ q ) De Morgans
Translation:
I went to McDonalds, but I did not get a Big Mac.


Im not sure if this is the right way to solve this problem does anyone know if this is right or wrong?

Thanks for your help!
 
Physics news on Phys.org
  • #2
That's right.

NOT("If I go to McD, then I get a Big Mac")
<=>
NOT("I don't go to McD" OR "I get a Big Mac")
<=>
NOT("I don't go to McD") AND NOT("I get a Big Mac")
<=>
"I go to McD" AND "I don't get a Big Mac"
<=>
"I go to McD and I don't get a Big Mac".
 

What are DeMorgan's laws and rules of logic?

DeMorgan's laws and rules of logic are mathematical principles that help us understand the relationship between logical statements. They are named after the mathematician Augustus De Morgan and are commonly used in fields such as computer science, mathematics, and philosophy.

What is the first DeMorgan's law?

The first DeMorgan's law states that the negation of a conjunction (AND) is equivalent to the disjunction (OR) of the negations of the individual statements. In other words, ¬(p ∧ q) is the same as (¬p) ∨ (¬q).

What is the second DeMorgan's law?

The second DeMorgan's law states that the negation of a disjunction (OR) is equivalent to the conjunction (AND) of the negations of the individual statements. In other words, ¬(p ∨ q) is the same as (¬p) ∧ (¬q).

How are DeMorgan's laws used in logic?

DeMorgan's laws are used to simplify logical statements and make them easier to understand. They can also be used to prove the validity or invalidity of an argument. By applying these laws, we can transform complex statements into simpler ones and determine if they are logically equivalent.

Can DeMorgan's laws be applied to more than two statements?

Yes, DeMorgan's laws can be applied to any number of statements, as long as they are connected by logical operators (AND, OR, NOT). For example, the negation of a conjunction of three statements (p ∧ q ∧ r) would be equivalent to the disjunction of the negations of those three statements (¬p ∨ ¬q ∨ ¬r).

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
970
  • Calculus and Beyond Homework Help
Replies
2
Views
2K
  • Calculus and Beyond Homework Help
Replies
2
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
Replies
3
Views
2K
  • Math Proof Training and Practice
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
11
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
4
Views
2K
  • Set Theory, Logic, Probability, Statistics
Replies
6
Views
3K
Back
Top