How to write statements with negation and disjunction in symbolic form?

  • Thread starter UrbanXrisis
  • Start date
In summary: This is because the negation of a disjunction (X V Y) is the conjunction of the negations (~X ^ ~Y). Therefore, the statement could also be written as ~(X V Y) or (~X ^ ~Y).
  • #1
UrbanXrisis
1,196
1

Homework Statement



This is just a simple logic question that I need a little guidance.
Let X= "I like cars"
Let Y= "I like trees"
Let ~ = not
Let V = or

How would this be written in symbols:
1. It is not the case that I like cars or I like trees
2. It is not the case that I like cars, or I like trees

Homework Equations



none

The Attempt at a Solution



1. ~X V Y
2. ~(X V Y)
 
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  • #2
your answers should be vice versa I think
 
  • #3
First statement: "It is not the case that: (I like cars or I like trees).

Second statement: (It is not the case that I like cars) or (it is not the case that I like trees).

I agree with theperthvan.
 
  • #4
that's what I thought, but the examples in the book gives the following:

P=Irene has red hair

PV~P = "Irene has red hair or she dos not have red hair"

if what you say is correct, then the example should say:

PV~P = "Irene has red hair, or she dos not have red hair"
 
  • #5
?? The only difference I see is a comma which, grammatically, is optional here. Both sentences mean the same thing.
 
  • #6
then shouldn't this be the same thing as well?
1. It is not the case that I like cars or I like trees
2. It is not the case that I like cars, or I like trees

Say X- I like cars and Y=I like trees
then using the example from the book
PV~P = "Irene has red hair or she dos not have red hair"

i could say ~X V Y, which would read: "I do not like cars or I like trees"

looking back at
1. It is not the case that I like cars or I like trees

would this be ~X V Y and not ~(X V Y)
 
  • #7
HallsofIvy said:
Second statement: (It is not the case that I like cars) or (it is not the case that I like trees).
The statement: "It is not the case that I like cars, or I like trees" also could read "(It is not the case that I like cars) or (It is the case that I like trees)".
 
Last edited:

Related to How to write statements with negation and disjunction in symbolic form?

What is a truth table?

A truth table is a table that shows the output of a logical expression based on all possible combinations of input values. It is used to determine the truth value of a complex statement.

Why are truth tables used?

Truth tables are used to analyze and evaluate the logical consistency and validity of complex statements or arguments. They help to determine whether a statement is true or false based on the given inputs.

How do you construct a truth table?

To construct a truth table, list all possible combinations of input values for the variables in the logical expression. Then, apply the logical operators (AND, OR, NOT) to these values to determine the output for each combination. The output values are then organized into a table format.

What is the purpose of using truth tables in science?

In science, truth tables are used to analyze the logical relationships between different variables or conditions in an experiment. They help to determine the validity of a hypothesis or the accuracy of a scientific theory.

Can truth tables be used for any type of logical expression?

Yes, truth tables can be used for any type of logical expression, as long as the expression is made up of logical operators (AND, OR, NOT) and variables that can have a truth value (true or false).

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